https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71086
Bug ID: 71086
Summary: miscompiled inline-asm + alternative constraints +
__builtin_expect + always_inline
Product: gcc
Version: 4.9.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: inline-asm
Assignee: unassigned at gcc dot gnu.org
Reporter: mirq-gccboogs at rere dot qmqm.pl
Target Milestone: ---
Created attachment 38474
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38474&action=edit
test case source
The attached code get's miscompiled when -DNO_EXPECT is not passed. With
__builtin_expect used, the operand to inline asm in inc_overflow() get's
replaced with uninitialized stack entry. This happens only with exact
combination of: -O1, inline-asm has multiple alternative constraints,
__builtin_expect is used in inc_overflow(), there are other not-optimized-out
variables on stack.
gcc versions 4.9.2 (-10 Debian) and 4.9.3 (-13ubuntu2) miscompile, gcc 5.3.1
generates correct code.
--- good: g++ -O1 -S -DNO_EXCEPT bug_inline.cc -o -
+++ bad: g++ -O1 -S bug_inline.cc -o -
@@ -5,55 +5,49 @@
_Z6test_smj:
.LFB2:
.cfi_startproc
- pushq %rbp
- .cfi_def_cfa_offset 16
- .cfi_offset 6, -16
pushq %rbx
- .cfi_def_cfa_offset 24
- .cfi_offset 3, -24
- subq $40, %rsp
+ .cfi_def_cfa_offset 16
+ .cfi_offset 3, -16
+ subq $48, %rsp
.cfi_def_cfa_offset 64
- movq %rdi, %rbp
+ movq %rdi, 8(%rsp)
movq %fs:40, %rax
- movq %rax, 24(%rsp)
+ movq %rax, 40(%rsp)
xorl %eax, %eax
cmpl $10, %esi
jbe .L2
movl %esi, %ebx
- leaq 8(%rsp), %rdi
+ leaq 24(%rsp), %rdi
call _Z3xdoRm
-.L5:
- movq %rbp, %rdi
+.L4:
#APP
# 18 "bug_inline.cpp" 1
- add %rbx, %rdi
+ add %rbx, 32(%rsp) <--- 32(%rsp) is not initialized, but
should be with 'v' (saved at 8(%rsp), or in %rbp in good code)
setc %sil
# 0 "" 2
#NO_APP
testb %sil, %sil
- movq $-1, %rax
- cmovne %rax, %rdi
- movq %rdi, 16(%rsp)
- leaq 16(%rsp), %rdi
+ je .L3
+ movq $-1, 32(%rsp)
+.L3:
+ leaq 32(%rsp), %rdi
call _Z3xdoRm
- movq 8(%rsp), %rax
- movq 24(%rsp), %rdx
+ movq 24(%rsp), %rax
+ movq 40(%rsp), %rdx
xorq %fs:40, %rdx
- je .L6
- jmp .L7
+ je .L5
+ jmp .L6
.L2:
- leaq 8(%rsp), %rdi
+ leaq 24(%rsp), %rdi
call _Z3xdoRm
movl $4294967295, %ebx
- jmp .L5
-.L7:
- call __stack_chk_fail
+ jmp .L4
.L6:
- addq $40, %rsp
- .cfi_def_cfa_offset 24
- popq %rbx
+ call __stack_chk_fail
+.L5:
+ addq $48, %rsp
.cfi_def_cfa_offset 16
- popq %rbp
+ popq %rbx
.cfi_def_cfa_offset 8
ret
.cfi_endproc
# Debian 4.9.2
$ gcc -v
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc-4.9.real
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.9.2-10'
--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.9 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i586 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.2 (Debian 4.9.2-10)
# Ubuntu 4.9.3
$ g++-4.9 -v
Using built-in specs.
COLLECT_GCC=g++-4.9
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.9.3-13ubuntu2'
--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.9 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.3 (Ubuntu 4.9.3-13ubuntu2)
