jarin updated this revision to Diff 376501.
jarin marked 5 inline comments as done.
jarin added a comment.

Addressed reviewer comments, separated merging of the abstract parameters into 
a function, prevented interleaving of parameters with locals.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D110571/new/

https://reviews.llvm.org/D110571

Files:
  lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
  lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
  lldb/test/API/functionalities/unused-inlined-parameters/Makefile
  
lldb/test/API/functionalities/unused-inlined-parameters/TestUnusedInlinedParameters.py
  lldb/test/API/functionalities/unused-inlined-parameters/main.c
  lldb/test/Shell/SymbolFile/DWARF/x86/Inputs/unused-inlined-params.s
  lldb/test/Shell/SymbolFile/DWARF/x86/unused-inlined-params.test

Index: lldb/test/Shell/SymbolFile/DWARF/x86/unused-inlined-params.test
===================================================================
--- /dev/null
+++ lldb/test/Shell/SymbolFile/DWARF/x86/unused-inlined-params.test
@@ -0,0 +1,48 @@
+# RUN: llvm-mc -filetype=obj %S/Inputs/unused-inlined-params.s \
+# RUN:         -triple x86_64-pc-linux -o %t.o
+# RUN: %lldb %t.o -s %s -o exit | FileCheck %s
+
+
+# In this test we verify that inlined functions still mention
+# all their parameters in `frame variable`, even when those
+# parameters were completely optimized away from the concrete
+# instance of the inlined function in the debug info.
+# The debugger should look up the parameters in the abstract
+# origin of the concrete instance.
+
+# Let us check that unused parameters of an inlined function are listed
+# at the inlined function entry.
+image lookup -v -s break_at_inlined_f_in_main
+# CHECK-LABEL: image lookup -v -s break_at_inlined_f_in_main
+# CHECK: name = "unused1", type = "void *", location = <empty>
+# CHECK: name = "used", type = "int", location = DW_OP_consts +42
+# CHECK: name = "unused2", type = "int", location = <empty>
+# CHECK: name = "partial", type = "int", location = DW_OP_reg4 RSI
+# CHECK: name = "unused3", type = "int", location = <empty>
+
+# Show variables outsid of the live range of the 'partial' parameter
+# and verify that the output is as expected.
+image lookup -v -s break_at_inlined_f_in_main_between_printfs
+# CHECK-LABEL: image lookup -v -s break_at_inlined_f_in_main_between_printfs
+# CHECK: name = "unused1", type = "void *", location = <empty>
+# CHECK: name = "used", type = "int", location = DW_OP_reg3 RBX
+# CHECK: name = "unused2", type = "int", location = <empty>
+# Note: image lookup does not show variables outside of their
+#       location, so |partial| is missing here.
+# CHECK-NOT: partial
+# CHECK: name = "unused3", type = "int", location = <empty>
+
+# Check that we show parameters even if all of them are compiled away.
+image lookup -v -s  break_at_inlined_g_in_main
+# CHECK-LABEL: image lookup -v -s  break_at_inlined_g_in_main
+# CHECK: name = "unused", type = "int", location = <empty>
+
+# Check that even the other inlined instance of f displays the correct
+# parameters.
+image lookup -v -s  break_at_inlined_f_in_other
+# CHECK-LABEL: image lookup -v -s  break_at_inlined_f_in_other
+# CHECK: name = "unused1", type = "void *", location = <empty>
+# CHECK: name = "used", type = "int", location = DW_OP_consts +1
+# CHECK: name = "unused2", type = "int", location = <empty>
+# CHECK: name = "partial", type = "int", location =  DW_OP_consts +2
+# CHECK: name = "unused3", type = "int", location = <empty>
Index: lldb/test/Shell/SymbolFile/DWARF/x86/Inputs/unused-inlined-params.s
===================================================================
--- /dev/null
+++ lldb/test/Shell/SymbolFile/DWARF/x86/Inputs/unused-inlined-params.s
@@ -0,0 +1,458 @@
+# The below program is roughly derived from the following C program.
+# To see the annotated debug info, look for the section 
+# '.section    .debug_info' below.
+#
+# __attribute__((always_inline))
+# void f(void* unused1, int used, int unused2, int partial, int unused3) {
+#   used += partial;
+#   printf("f %i", partial);
+#   printf("f %i", used);   // |partial| is not live at this line.
+# }
+#
+# void g(int unused) {
+#   printf("Hello");
+# }
+#
+# __attribute__((noinline))
+# void other() {
+#   f(nullptr, 1, 0, 2, 0);
+# }
+#
+# int main(int argc, char** argv) {
+#   f(argv, 42, 1, argc, 2);
+#   g(1);
+#   other();
+#   return 0;
+# }
+
+    .text
+    .file    "unused-inlined-params.c"
+
+.Lcu_begin:
+
+    .globl    other
+other:
+    nop
+.Linlined_f_in_other:
+break_at_inlined_f_in_other:
+    callq    printf        # Omitted the setup of arguments.
+.Linlined_f_in_other_between_printfs:
+    callq    printf        # Omitted the setup of arguments.
+.Linlined_f_in_other_end:
+    retq
+.Lother_end:
+    .size    other, .Lother_end-other
+
+    .globl    main
+main:
+    .file    1 "/example" "unused-inlined-params.c"
+    movl    $1, %esi
+.Linlined_f:
+break_at_inlined_f_in_main:
+    leal    42(%rsi), %ebx
+.Linlined_f_before_printf:
+    callq    printf        # Omitted the setup of arguments.
+.Linlined_f_between_printfs:
+break_at_inlined_f_in_main_between_printfs:
+    callq    printf        # Omitted the setup of arguments.
+.Linlined_f_end:
+.Linlined_g:
+break_at_inlined_g_in_main:
+    callq    printf        # Omitted the setup of arguments.
+.Linlined_g_end:
+    callq    other
+    retq
+.Lmain_end:
+    .size    main, .Lmain_end-main
+
+# Dummy printf implementation.
+printf:
+    retq
+
+# Simple entry point to make the linker happy.
+    .globl  _start
+_start:
+    jmp     main
+
+.Lcu_end:
+
+
+    .section    .debug_loc,"",@progbits
+.Ldebug_loc_partial:
+    .quad    .Linlined_f-.Lcu_begin
+    .quad    .Linlined_f_between_printfs-.Lcu_begin
+    .short   1                               # Loc expr size
+    .byte    84                              # super-register DW_OP_reg4
+    .quad    0
+    .quad    0
+.Ldebug_loc_used:
+    .quad    .Linlined_f-.Lcu_begin
+    .quad    .Linlined_f_before_printf-.Lcu_begin
+    .short   3                               # Loc expr size
+    .byte    17                              # DW_OP_consts
+    .byte    42                              # value
+    .byte    159                             # DW_OP_stack_value
+    .quad    .Linlined_f_before_printf-.Lcu_begin
+    .quad    .Linlined_f_end-.Lcu_begin
+    .short   1                               # Loc expr size
+    .byte    83                              # super-register DW_OP_reg3
+    .quad    0
+    .quad    0
+.Ldebug_loc_partial_in_other:
+    .quad    .Linlined_f_in_other-.Lcu_begin
+    .quad    .Linlined_f_in_other_between_printfs-.Lcu_begin
+    .short   3                               # Loc expr size
+    .byte    17                              # DW_OP_consts
+    .byte    2                               # value
+    .byte    159                             # DW_OP_stack_value
+    .quad    0
+    .quad    0
+.Ldebug_loc_used_in_other:
+    .quad    .Linlined_f_in_other-.Lcu_begin
+    .quad    .Linlined_f_in_other_end-.Lcu_begin
+    .short   3                               # Loc expr size
+    .byte    17                              # DW_OP_consts
+    .byte    1                               # value
+    .byte    159                             # DW_OP_stack_value
+    .quad    0
+    .quad    0
+
+    .section    .debug_abbrev,"",@progbits
+    .byte    1                               # Abbreviation Code
+    .byte    17                              # DW_TAG_compile_unit
+    .byte    1                               # DW_CHILDREN_yes
+    .byte    3                               # DW_AT_name
+    .byte    14                              # DW_FORM_strp
+    .byte    16                              # DW_AT_stmt_list
+    .byte    23                              # DW_FORM_sec_offset
+    .byte    17                              # DW_AT_low_pc
+    .byte    1                               # DW_FORM_addr
+    .byte    18                              # DW_AT_high_pc
+    .byte    6                               # DW_FORM_data4
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    4                               # Abbreviation Code
+    .byte    5                               # DW_TAG_formal_parameter
+    .byte    0                               # DW_CHILDREN_no
+    .byte    2                               # DW_AT_location
+    .byte    23                              # DW_FORM_sec_offset
+    .byte    49                              # DW_AT_abstract_origin
+    .byte    19                              # DW_FORM_ref4
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    5                               # Abbreviation Code
+    .byte    46                              # DW_TAG_subprogram
+    .byte    1                               # DW_CHILDREN_yes
+    .byte    3                               # DW_AT_name
+    .byte    14                              # DW_FORM_strp
+    .byte    58                              # DW_AT_decl_file
+    .byte    11                              # DW_FORM_data1
+    .byte    59                              # DW_AT_decl_line
+    .byte    11                              # DW_FORM_data1
+    .byte    39                              # DW_AT_prototyped
+    .byte    25                              # DW_FORM_flag_present
+    .byte    63                              # DW_AT_external
+    .byte    25                              # DW_FORM_flag_present
+    .byte    32                              # DW_AT_inline
+    .byte    11                              # DW_FORM_data1
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    6                               # Abbreviation Code
+    .byte    5                               # DW_TAG_formal_parameter
+    .byte    0                               # DW_CHILDREN_no
+    .byte    3                               # DW_AT_name
+    .byte    14                              # DW_FORM_strp
+    .byte    58                              # DW_AT_decl_file
+    .byte    11                              # DW_FORM_data1
+    .byte    59                              # DW_AT_decl_line
+    .byte    11                              # DW_FORM_data1
+    .byte    73                              # DW_AT_type
+    .byte    19                              # DW_FORM_ref4
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    7                               # Abbreviation Code
+    .byte    15                              # DW_TAG_pointer_type
+    .byte    0                               # DW_CHILDREN_no
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    8                               # Abbreviation Code
+    .byte    36                              # DW_TAG_base_type
+    .byte    0                               # DW_CHILDREN_no
+    .byte    3                               # DW_AT_name
+    .byte    14                              # DW_FORM_strp
+    .byte    62                              # DW_AT_encoding
+    .byte    11                              # DW_FORM_data1
+    .byte    11                              # DW_AT_byte_size
+    .byte    11                              # DW_FORM_data1
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    9                               # Abbreviation Code
+    .byte    46                              # DW_TAG_subprogram
+    .byte    1                               # DW_CHILDREN_yes
+    .byte    17                              # DW_AT_low_pc
+    .byte    1                               # DW_FORM_addr
+    .byte    18                              # DW_AT_high_pc
+    .byte    6                               # DW_FORM_data4
+    .byte    64                              # DW_AT_frame_base
+    .byte    24                              # DW_FORM_exprloc
+    .byte    3                               # DW_AT_name
+    .byte    14                              # DW_FORM_strp
+    .byte    58                              # DW_AT_decl_file
+    .byte    11                              # DW_FORM_data1
+    .byte    59                              # DW_AT_decl_line
+    .byte    11                              # DW_FORM_data1
+    .byte    39                              # DW_AT_prototyped
+    .byte    25                              # DW_FORM_flag_present
+    .byte    73                              # DW_AT_type
+    .byte    19                              # DW_FORM_ref4
+    .byte    63                              # DW_AT_external
+    .byte    25                              # DW_FORM_flag_present
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    10                              # Abbreviation Code
+    .byte    5                               # DW_TAG_formal_parameter
+    .byte    0                               # DW_CHILDREN_no
+    .byte    2                               # DW_AT_location
+    .byte    23                              # DW_FORM_sec_offset
+    .byte    3                               # DW_AT_name
+    .byte    14                              # DW_FORM_strp
+    .byte    58                              # DW_AT_decl_file
+    .byte    11                              # DW_FORM_data1
+    .byte    59                              # DW_AT_decl_line
+    .byte    11                              # DW_FORM_data1
+    .byte    73                              # DW_AT_type
+    .byte    19                              # DW_FORM_ref4
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    11                              # Abbreviation Code
+    .byte    29                              # DW_TAG_inlined_subroutine
+    .byte    1                               # DW_CHILDREN_yes
+    .byte    49                              # DW_AT_abstract_origin
+    .byte    19                              # DW_FORM_ref4
+    .byte    17                              # DW_AT_low_pc
+    .byte    1                               # DW_FORM_addr
+    .byte    18                              # DW_AT_high_pc
+    .byte    6                               # DW_FORM_data4
+    .byte    88                              # DW_AT_call_file
+    .byte    11                              # DW_FORM_data1
+    .byte    89                              # DW_AT_call_line
+    .byte    11                              # DW_FORM_data1
+    .byte    87                              # DW_AT_call_column
+    .byte    11                              # DW_FORM_data1
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+
+    .byte    12                              # Abbreviation Code
+    .byte    15                              # DW_TAG_pointer_type
+    .byte    0                               # DW_CHILDREN_no
+    .byte    73                              # DW_AT_type
+    .byte    19                              # DW_FORM_ref4
+    .byte    0                               # EOM(1)
+    .byte    0                               # EOM(2)
+    .byte    0                               # EOM(3)
+
+    .section    .debug_info,"",@progbits
+.Ldi_cu_begin:
+    .long    .Ldebug_info_end0-.Ldebug_info_start0 # Length of Unit
+.Ldebug_info_start0:
+    .short    4                              # DWARF version number
+    .long    .debug_abbrev                   # Offset Into Abbrev. Section
+    .byte    8                               # Address Size (in bytes)
+    .byte    1                               # Abbrev [1] DW_TAG_compile_unit
+    .long    .Linfo_string_fname             #   DW_AT_name
+    .long    .Lline_table_start0             #   DW_AT_stmt_list
+    .quad    .Lcu_begin                      #   DW_AT_low_pc
+    .long    .Lcu_end-.Lcu_begin             #   DW_AT_high_pc
+
+# Debug info for |f| (abstract version with all parameters).
+
+.Ldebug_info_f:
+    .byte    5                               #   Abbrev [5] DW_TAG_subprogram
+    .long    .Linfo_string_f                 #     DW_AT_name
+    .byte    1                               #     DW_AT_decl_file
+    .byte    4                               #     DW_AT_decl_line
+                                             #     DW_AT_prototyped
+                                             #     DW_AT_external
+    .byte    1                               #     DW_AT_inline
+.Ldebug_info_param1:
+    .byte    6                               #     Abbrev [6] DW_TAG_formal_parameter
+    .long    .Linfo_string_unused1           #       DW_AT_name
+    .byte    1                               #       DW_AT_decl_file
+    .byte    4                               #       DW_AT_decl_line
+    .long    .Ldebug_info_void_ptr-.Ldi_cu_begin
+                                             #       DW_AT_type
+.Ldebug_info_param2:
+    .byte    6                               #     Abbrev [6] DW_TAG_formal_parameter
+    .long    .Linfo_string_used              #       DW_AT_name
+    .byte    1                               #       DW_AT_decl_file
+    .byte    4                               #       DW_AT_decl_line
+    .long    .Ldebug_info_int-.Ldi_cu_begin  #       DW_AT_type
+.Ldebug_info_param3:
+    .byte    6                               #     Abbrev [6] DW_TAG_formal_parameter
+    .long    .Linfo_string_unused2           #       DW_AT_name
+    .byte    1                               #       DW_AT_decl_file
+    .byte    4                               #       DW_AT_decl_line
+    .long    .Ldebug_info_int-.Ldi_cu_begin  #       DW_AT_type
+.Ldebug_info_param4:
+    .byte    6                               #     Abbrev [6] DW_TAG_formal_parameter
+    .long    .Linfo_string_partial           #       DW_AT_name
+    .byte    1                               #       DW_AT_decl_file
+    .byte    4                               #       DW_AT_decl_line
+    .long    .Ldebug_info_int-.Ldi_cu_begin  #       DW_AT_type
+.Ldebug_info_param5:
+    .byte    6                               #     Abbrev [6] DW_TAG_formal_parameter
+    .long    .Linfo_string_unused3           #       DW_AT_name
+    .byte    1                               #       DW_AT_decl_file
+    .byte    4                               #       DW_AT_decl_line
+    .long    .Ldebug_info_int-.Ldi_cu_begin  #       DW_AT_type
+    .byte    0                               #   End Of Children Mark (DW_TAG_subprogram)
+
+# Debug info for |g| (abstract version with all parameters).
+
+.Ldebug_info_g:
+    .byte    5                               #   Abbrev [5] DW_TAG_subprogram
+    .long    .Linfo_string_g                 #     DW_AT_name
+    .byte    1                               #     DW_AT_decl_file
+    .byte    4                               #     DW_AT_decl_line
+                                             #     DW_AT_prototyped
+                                             #     DW_AT_external
+    .byte    1                               #     DW_AT_inline
+.Ldebug_info_g_param1:
+    .byte    6                               #     Abbrev [6] DW_TAG_formal_parameter
+    .long    .Linfo_string_unused            #       DW_AT_name
+    .byte    1                               #       DW_AT_decl_file
+    .byte    10                              #       DW_AT_decl_line
+    .long    .Ldebug_info_int-.Ldi_cu_begin
+    .byte    0                               #   End Of Children Mark (DW_TAG_subprogram)
+
+# Debug info for |main|.
+
+    .byte    9                               #   Abbrev [9] DW_TAG_subprogram
+    .quad    main                            #     DW_AT_low_pc
+    .long    .Lmain_end-main                 #     DW_AT_high_pc
+    .byte    1                               #     DW_AT_frame_base
+    .byte    87
+    .long    .Linfo_string_main              #     DW_AT_name
+    .byte    1                               #     DW_AT_decl_file
+    .byte    18                              #     DW_AT_decl_line
+                                             #     DW_AT_prototyped
+    .long    .Ldebug_info_int-.Ldi_cu_begin  #     DW_AT_type
+                                             #     DW_AT_external
+
+#   Debug info for concrete |f| inlined into |main|.
+
+    .byte    11                              #     Abbrev [11] DW_TAG_inlined_subroutine
+    .long    .Ldebug_info_f-.Ldi_cu_begin
+                                             #       DW_AT_abstract_origin
+    .quad    .Linlined_f                     #       DW_AT_low_pc
+    .long    .Linlined_f_end-.Linlined_f     #       DW_AT_high_pc
+    .byte    1                               #       DW_AT_call_file
+    .byte    20                              #       DW_AT_call_line
+    .byte    3                               #       DW_AT_call_column
+    .byte    4                               #       Abbrev [4] DW_TAG_formal_parameter
+    .long    .Ldebug_loc_used                #         DW_AT_location
+    .long    .Ldebug_info_param2-.Ldi_cu_begin
+                                             #         DW_AT_abstract_origin
+    .byte    4                               #       Abbrev [4] DW_TAG_formal_parameter
+    .long    .Ldebug_loc_partial             #         DW_AT_location
+    .long    .Ldebug_info_param4-.Ldi_cu_begin
+                                             #         DW_AT_abstract_origin
+    .byte    0                               #     End Of Children Mark (DW_TAG_inlined_subroutine)
+
+#   Debug info for concrete |g| inlined into |main|.
+
+    .byte    11                              #     Abbrev [11] DW_TAG_inlined_subroutine
+    .long    .Ldebug_info_g-.Ldi_cu_begin
+                                             #       DW_AT_abstract_origin
+    .quad    .Linlined_g                     #       DW_AT_low_pc
+    .long    .Linlined_g_end-.Linlined_g     #       DW_AT_high_pc
+    .byte    1                               #       DW_AT_call_file
+    .byte    21                              #       DW_AT_call_line
+    .byte    3                               #       DW_AT_call_column
+    .byte    0                               #     End Of Children Mark (DW_TAG_inlined_subroutine)
+
+    .byte    0                               #   End Of Children Mark (DW_TAG_subprogram)
+
+# Debug info for |other|.
+
+    .byte    9                               #   Abbrev [9] DW_TAG_subprogram
+    .quad    other                           #     DW_AT_low_pc
+    .long    .Lother_end-other               #     DW_AT_high_pc
+    .byte    1                               #     DW_AT_frame_base
+    .byte    87
+    .long    .Linfo_string_other             #     DW_AT_name
+    .byte    1                               #     DW_AT_decl_file
+    .byte    15                              #     DW_AT_decl_line
+                                             #     DW_AT_prototyped
+    .long    .Ldebug_info_int-.Ldi_cu_begin  #     DW_AT_type
+                                             #     DW_AT_external
+
+#   Debug info for concrete |f| inlined into |other|.
+
+    .byte    11                              #     Abbrev [11] DW_TAG_inlined_subroutine
+    .long    .Ldebug_info_f-.Ldi_cu_begin
+                                             #       DW_AT_abstract_origin
+    .quad    .Linlined_f_in_other            #       DW_AT_low_pc
+    .long    .Linlined_f_in_other_end-.Linlined_f_in_other
+                                             #       DW_AT_high_pc
+    .byte    1                               #       DW_AT_call_file
+    .byte    16                              #       DW_AT_call_line
+    .byte    3                               #       DW_AT_call_column
+    .byte    4                               #       Abbrev [4] DW_TAG_formal_parameter
+    .long    .Ldebug_loc_used_in_other       #         DW_AT_location
+    .long    .Ldebug_info_param2-.Ldi_cu_begin
+                                             #         DW_AT_abstract_origin
+    .byte    4                               #       Abbrev [4] DW_TAG_formal_parameter
+    .long    .Ldebug_loc_partial_in_other    #         DW_AT_location
+    .long    .Ldebug_info_param4-.Ldi_cu_begin
+                                             #         DW_AT_abstract_origin
+    .byte    0                               #     End Of Children Mark (DW_TAG_inlined_subroutine)
+    .byte    0                               #   End Of Children Mark (DW_TAG_subprogram)
+
+.Ldebug_info_void_ptr:
+    .byte    7                               #   Abbrev [7] DW_TAG_pointer_type
+.Ldebug_info_int:
+    .byte    8                               #   Abbrev [8] DW_TAG_base_type
+    .long    .Linfo_string_int               #     DW_AT_name
+    .byte    5                               #     DW_AT_encoding
+    .byte    4                               #     DW_AT_byte_size
+
+    .byte    0                               # End Of Children Mark (DW_TAG_compile_unit)
+.Ldebug_info_end0:
+    .section    .debug_str,"MS",@progbits,1
+.Linfo_string_fname:
+    .asciz    "unused-inlined-params.c"
+.Linfo_string_f:
+    .asciz    "f"
+.Linfo_string_unused1:
+    .asciz    "unused1"
+.Linfo_string_used:
+    .asciz    "used"
+.Linfo_string_int:
+    .asciz    "int"
+.Linfo_string_unused2:
+    .asciz    "unused2"
+.Linfo_string_partial:
+    .asciz    "partial"
+.Linfo_string_unused3:
+    .asciz    "unused3"
+.Linfo_string_main:
+    .asciz    "main"
+.Linfo_string_g:
+    .asciz    "g"
+.Linfo_string_unused:
+    .asciz    "unused"
+.Linfo_string_other:
+    .asciz    "other"
+    .section    ".note.GNU-stack","",@progbits
+    .addrsig
+    .section    .debug_line,"",@progbits
+.Lline_table_start0:
Index: lldb/test/API/functionalities/unused-inlined-parameters/main.c
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/unused-inlined-parameters/main.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+__attribute__((always_inline))
+void f(void* unused1, int used, int unused2) {
+  printf("f %i", used);  // break here
+}
+
+int main(int argc, char** argv) {
+  f(argv, 42, 1);
+  return 0;
+}
Index: lldb/test/API/functionalities/unused-inlined-parameters/TestUnusedInlinedParameters.py
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/unused-inlined-parameters/TestUnusedInlinedParameters.py
@@ -0,0 +1,20 @@
+"""
+Test that unused inlined parameters are displayed.
+"""
+
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestUnusedInlinedParameters(TestBase):
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test_unused_inlined_parameters(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "// break here", lldb.SBFileSpec("main.c"))
+
+        # For the unused parameters, only check the types.
+        self.assertEqual("void *", self.frame().FindVariable("unused1").GetType().GetName())
+        self.assertEqual(42, self.frame().FindVariable("used").GetValueAsUnsigned())
+        self.assertEqual("int", self.frame().FindVariable("unused2").GetType().GetName())
Index: lldb/test/API/functionalities/unused-inlined-parameters/Makefile
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/unused-inlined-parameters/Makefile
@@ -0,0 +1,4 @@
+C_SOURCES := main.c
+CFLAGS_EXTRAS := -O1
+
+include Makefile.rules
Index: lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
+++ lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h
@@ -379,6 +379,8 @@
   lldb::VariableSP ParseVariableDIE(const lldb_private::SymbolContext &sc,
                                     const DWARFDIE &die,
                                     const lldb::addr_t func_low_pc);
+  lldb::VariableSP ParseVariableDIECached(const lldb_private::SymbolContext &sc,
+                                          const DWARFDIE &die);
 
   void
   ParseAndAppendGlobalVariable(const lldb_private::SymbolContext &sc,
@@ -392,7 +394,13 @@
   size_t ParseVariablesInFunctionContextRecursive(
       const lldb_private::SymbolContext &sc, const DWARFDIE &die,
       const lldb::addr_t func_low_pc,
-      lldb_private::VariableList &variable_list);
+      llvm::SmallVectorImpl<DWARFDIE> &accumulator);
+
+  size_t PopulateBlockVariableList(
+      lldb_private::VariableList &variable_list,
+      const lldb_private::SymbolContext &sc,
+      const llvm::SmallVectorImpl<DWARFDIE> &variable_dies,
+      const lldb::addr_t func_low_pc);
 
   bool ClassOrStructIsVirtual(const DWARFDIE &die);
 
Index: lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -3071,8 +3071,7 @@
 
         m_index->GetGlobalVariables(
             dwarf_cu->GetNonSkeletonUnit(), [&](DWARFDIE die) {
-              VariableSP var_sp(
-                  ParseVariableDIE(sc, die, LLDB_INVALID_ADDRESS));
+              VariableSP var_sp(ParseVariableDIECached(sc, die));
               if (var_sp) {
                 variables->AddVariableIfUnique(var_sp);
                 ++vars_added;
@@ -3086,6 +3085,26 @@
   return 0;
 }
 
+VariableSP SymbolFileDWARF::ParseVariableDIECached(const SymbolContext &sc,
+                                                   const DWARFDIE &die) {
+  if (!die)
+    return nullptr;
+
+  DIEToVariableSP &die_to_variable = die.GetDWARF()->GetDIEToVariable();
+
+  VariableSP var_sp = die_to_variable[die.GetDIE()];
+  if (var_sp)
+    return var_sp;
+
+  var_sp = ParseVariableDIE(sc, die, LLDB_INVALID_ADDRESS);
+  if (var_sp) {
+    die_to_variable[die.GetDIE()] = var_sp;
+    if (DWARFDIE spec_die = die.GetReferencedDIE(DW_AT_specification))
+      die_to_variable[spec_die.GetDIE()] = var_sp;
+  }
+  return var_sp;
+}
+
 VariableSP SymbolFileDWARF::ParseVariableDIE(const SymbolContext &sc,
                                              const DWARFDIE &die,
                                              const lldb::addr_t func_low_pc) {
@@ -3095,9 +3114,6 @@
   if (!die)
     return nullptr;
 
-  if (VariableSP var_sp = GetDIEToVariable()[die.GetDIE()])
-    return var_sp; // Already been parsed!
-
   const dw_tag_t tag = die.Tag();
   ModuleSP module = GetObjectFile()->GetModule();
 
@@ -3107,8 +3123,6 @@
 
   DWARFAttributes attributes;
   const size_t num_attributes = die.GetAttributes(attributes);
-  DWARFDIE spec_die;
-  VariableSP var_sp;
   const char *name = nullptr;
   const char *mangled = nullptr;
   Declaration decl;
@@ -3155,9 +3169,6 @@
     case DW_AT_location:
       location_form = form_value;
       break;
-    case DW_AT_specification:
-      spec_die = form_value.Reference();
-      break;
     case DW_AT_start_scope:
       // TODO: Implement this.
       break;
@@ -3168,6 +3179,7 @@
     case DW_AT_description:
     case DW_AT_endianity:
     case DW_AT_segment:
+    case DW_AT_specification:
     case DW_AT_visibility:
     default:
     case DW_AT_abstract_origin:
@@ -3360,7 +3372,7 @@
             location.Update_DW_OP_addr(exe_file_addr);
           } else {
             // Variable didn't make it into the final executable
-            return var_sp;
+            return nullptr;
           }
         }
       }
@@ -3406,35 +3418,25 @@
     }
   }
 
-  if (symbol_context_scope) {
-    auto type_sp = std::make_shared<SymbolFileType>(
-        *this, GetUID(type_die_form.Reference()));
-
-    if (use_type_size_for_value && type_sp->GetType())
-      location.UpdateValue(
-          const_value_form.Unsigned(),
-          type_sp->GetType()->GetByteSize(nullptr).getValueOr(0),
-          die.GetCU()->GetAddressByteSize());
-
-    var_sp = std::make_shared<Variable>(
-        die.GetID(), name, mangled, type_sp, scope, symbol_context_scope,
-        scope_ranges, &decl, location, is_external, is_artificial,
-        location_is_const_value_data, is_static_member);
-  } else {
+  if (!symbol_context_scope) {
     // Not ready to parse this variable yet. It might be a global or static
     // variable that is in a function scope and the function in the symbol
     // context wasn't filled in yet
-    return var_sp;
+    return nullptr;
   }
-  // Cache var_sp even if NULL (the variable was just a specification or was
-  // missing vital information to be able to be displayed in the debugger
-  // (missing location due to optimization, etc)) so we don't re-parse this
-  // DIE over and over later...
-  GetDIEToVariable()[die.GetDIE()] = var_sp;
-  if (spec_die)
-    GetDIEToVariable()[spec_die.GetDIE()] = var_sp;
 
-  return var_sp;
+  auto type_sp = std::make_shared<SymbolFileType>(
+      *this, GetUID(type_die_form.Reference()));
+
+  if (use_type_size_for_value && type_sp->GetType())
+    location.UpdateValue(const_value_form.Unsigned(),
+                         type_sp->GetType()->GetByteSize(nullptr).getValueOr(0),
+                         die.GetCU()->GetAddressByteSize());
+
+  return std::make_shared<Variable>(
+      die.GetID(), name, mangled, type_sp, scope, symbol_context_scope,
+      scope_ranges, &decl, location, is_external, is_artificial,
+      location_is_const_value_data, is_static_member);
 }
 
 DWARFDIE
@@ -3498,7 +3500,9 @@
     return;
   }
 
-  // We haven't already parsed it, lets do that now.
+  // We haven't parsed the variable yet, lets do that now. Also, let us include
+  // the variable in the relevant compilation unit's variable list, if it
+  // exists.
   VariableListSP variable_list_sp;
   DWARFDIE sc_parent_die = GetParentSymbolContextDIE(die);
   dw_tag_t parent_tag = sc_parent_die.Tag();
@@ -3525,7 +3529,7 @@
     return;
   }
 
-  var_sp = ParseVariableDIE(sc, die, LLDB_INVALID_ADDRESS);
+  var_sp = ParseVariableDIECached(sc, die);
   if (!var_sp)
     return;
 
@@ -3534,33 +3538,115 @@
     variable_list_sp->AddVariableIfUnique(var_sp);
 }
 
+namespace {
+
+using DIEVector = llvm::SmallVector<DWARFDIE, 2>;
+
+DIEVector MergeBlockAbstractParameters(const DWARFDIE &block_die,
+                                       DIEVector &&variable_dies) {
+  // DW_TAG_inline_subroutine objects may omit DW_TAG_formal_parameter in
+  // instances of the function when they are unused (i.e., the parameter's
+  // location list would be empty). The current DW_TAG_inline_subroutine may
+  // refer to another DW_TAG_subprogram that might actually have the definitions
+  // of the parameters and we need to include these so they show up in the
+  // variables for this function (for example, in a stack trace). Let us try to
+  // find the abstract subprogram that might contain the parameter definitions
+  // and merge with the concrete parameters.
+
+  // Nothing to merge if the block is not an inlined function.
+  if (block_die.Tag() != DW_TAG_inlined_subroutine) {
+    return std::move(variable_dies);
+  }
+
+  // Nothing to merge if the block does not have abstract parameters.
+  DWARFDIE abs_die = block_die.GetReferencedDIE(DW_AT_abstract_origin);
+  if (!abs_die || abs_die.Tag() != DW_TAG_subprogram ||
+      !abs_die.HasChildren()) {
+    return std::move(variable_dies);
+  }
+
+  // For each abstract parameter, if we have its concrete counterpart, insert
+  // it. Otherwise, insert the abstract parameter.
+  DIEVector::iterator concrete_it = variable_dies.begin();
+  DWARFDIE abstract_child = abs_die.GetFirstChild();
+  DIEVector merged;
+  bool did_merge_abstract = false;
+  for (; abstract_child; abstract_child = abstract_child.GetSibling()) {
+    if (abstract_child.Tag() == DW_TAG_formal_parameter) {
+      if (concrete_it == variable_dies.end() ||
+          concrete_it->Tag() != DW_TAG_formal_parameter) {
+        // We arrived at the end of the concrete parameter list, so all
+        // the remaining abstract parameters must have been omitted.
+        // Let us insert them to the merged list here.
+        merged.push_back(abstract_child);
+        did_merge_abstract = true;
+        continue;
+      }
+
+      DWARFDIE origin_of_concrete =
+          concrete_it->GetReferencedDIE(DW_AT_abstract_origin);
+      if (origin_of_concrete && origin_of_concrete == abstract_child) {
+        // The current abstract paramater is the origin of the current
+        // concrete parameter, just push the concrete parameter.
+        merged.push_back(*concrete_it);
+        ++concrete_it;
+      } else {
+        // Otherwise, the parameter must have been omitted from the concrete
+        // function, so insert the abstract one.
+        merged.push_back(abstract_child);
+        did_merge_abstract = true;
+      }
+    }
+  }
+
+  // Shortcut if no merging happened.
+  if (!did_merge_abstract)
+    return std::move(variable_dies);
+
+  // We inserted all the abstract parameters (or their concrete counterparts).
+  // Let us insert all the remaining concrete variables to the merged list.
+  // During the insertion, let us check there are no remaining concrete
+  // formal parameters. If that's the case, then just bailout from the merge -
+  // the variable list is malformed.
+  for (; concrete_it != variable_dies.end(); ++concrete_it) {
+    if (concrete_it->Tag() == DW_TAG_formal_parameter) {
+      return std::move(variable_dies);
+    }
+    merged.push_back(*concrete_it);
+  }
+  return std::move(merged);
+}
+
+} // namespace
+
 size_t SymbolFileDWARF::ParseVariablesInFunctionContext(
     const SymbolContext &sc, const DWARFDIE &die,
     const lldb::addr_t func_low_pc) {
   if (!die || !sc.function)
     return 0;
 
-  Block *block =
-      sc.function->GetBlock(/*can_create=*/true).FindBlockByID(die.GetID());
-  const bool can_create = false;
-  VariableListSP variable_list_sp = block->GetBlockVariableList(can_create);
+  DIEVector dummy_block_variables; // The recursive call should not add anything
+                                   // to this vector because |die| should be a
+                                   // subprogram, so all variables will be added
+                                   // to the subprogram's list.
   return ParseVariablesInFunctionContextRecursive(sc, die, func_low_pc,
-                                                  *variable_list_sp);
+                                                  dummy_block_variables);
 }
 
+// This method parses all the variables in the blocks in the subtree of |die|,
+// and inserts them to the variable list for all the nested blocks.
+// The uninserted variables for the current block are accumulated in
+// |accumulator|.
 size_t SymbolFileDWARF::ParseVariablesInFunctionContextRecursive(
     const lldb_private::SymbolContext &sc, const DWARFDIE &die,
-    const lldb::addr_t func_low_pc, VariableList &variable_list) {
+    const lldb::addr_t func_low_pc,
+    llvm::SmallVectorImpl<DWARFDIE> &accumulator) {
   size_t vars_added = 0;
   dw_tag_t tag = die.Tag();
 
   if ((tag == DW_TAG_variable) || (tag == DW_TAG_constant) ||
       (tag == DW_TAG_formal_parameter)) {
-    VariableSP var_sp(ParseVariableDIE(sc, die, func_low_pc));
-    if (var_sp) {
-      variable_list.AddVariableIfUnique(var_sp);
-      ++vars_added;
-    }
+    accumulator.push_back(die);
   }
 
   switch (tag) {
@@ -3592,29 +3678,46 @@
       block_variable_list_sp = std::make_shared<VariableList>();
       block->SetVariableList(block_variable_list_sp);
     }
+
+    llvm::SmallVector<DWARFDIE, 2> block_variables;
     for (DWARFDIE child = die.GetFirstChild(); child;
          child = child.GetSibling()) {
       vars_added += ParseVariablesInFunctionContextRecursive(
-          sc, child, func_low_pc, *block_variable_list_sp);
+          sc, child, func_low_pc, block_variables);
     }
-
+    block_variables =
+        MergeBlockAbstractParameters(die, std::move(block_variables));
+    vars_added += PopulateBlockVariableList(*block_variable_list_sp, sc,
+                                            block_variables, func_low_pc);
     break;
   }
 
   default:
-    // Recurse to children with the same variable list.
+    // Recurse to children with the same variable accumulator.
     for (DWARFDIE child = die.GetFirstChild(); child;
          child = child.GetSibling()) {
       vars_added += ParseVariablesInFunctionContextRecursive(
-          sc, child, func_low_pc, variable_list);
+          sc, child, func_low_pc, accumulator);
     }
-
     break;
   }
 
   return vars_added;
 }
 
+size_t SymbolFileDWARF::PopulateBlockVariableList(
+    VariableList &variable_list, const lldb_private::SymbolContext &sc,
+    const llvm::SmallVectorImpl<DWARFDIE> &variable_dies,
+    const lldb::addr_t func_low_pc) {
+  // Parse the variable DIEs and insert them to the list.
+  for (auto &die : variable_dies) {
+    if (VariableSP var_sp = ParseVariableDIE(sc, die, func_low_pc)) {
+      variable_list.AddVariableIfUnique(var_sp);
+    }
+  }
+  return variable_dies.size();
+}
+
 /// Collect call site parameters in a DW_TAG_call_site DIE.
 static CallSiteParameterArray
 CollectCallSiteParameters(ModuleSP module, DWARFDIE call_site_die) {
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