t.p.northover created this revision.
Herald added a subscriber: mcrosier.
The size of an os_log buffer is known at any stage of compilation, so making it
a constant expression means that the common idiom of declaring a buffer for it
won't result in a VLA. That allows the compiler to skip saving and restoring
the stack pointer around such buffers.
There can be hundreds or even thousands of such calls, even in firmware
projects, so the code size savings add up.
Repository:
rC Clang
https://reviews.llvm.org/D53514
Files:
clang/lib/AST/ExprConstant.cpp
clang/lib/CodeGen/CGBuiltin.cpp
clang/test/CodeGen/builtins.c
Index: clang/test/CodeGen/builtins.c
===================================================================
--- clang/test/CodeGen/builtins.c
+++ clang/test/CodeGen/builtins.c
@@ -729,25 +729,28 @@
// CHECK-LABEL: define void @test_builtin_os_log_errno
void test_builtin_os_log_errno() {
- // CHECK: %[[VLA:.*]] = alloca i8, i64 4, align 16
- // CHECK: call void @__os_log_helper_16_2_1_0_96(i8* %[[VLA]])
+ // CHECK-NOT: @stacksave
+ // CHECK: %[[BUF:.*]] = alloca [4 x i8], align 1
+ // CHECK: %[[DECAY:.*]] = getelementptr inbounds [4 x i8], [4 x i8]*
%[[BUF]], i32 0, i32 0
+ // CHECK: call void @__os_log_helper_1_2_1_0_96(i8* %[[DECAY]])
+ // CHECK-NOT: @stackrestore
char buf[__builtin_os_log_format_buffer_size("%m")];
__builtin_os_log_format(buf, "%m");
}
-// CHECK-LABEL: define linkonce_odr hidden void @__os_log_helper_16_2_1_0_96
+// CHECK-LABEL: define linkonce_odr hidden void @__os_log_helper_1_2_1_0_96
// CHECK: (i8* %[[BUFFER:.*]])
// CHECK: %[[BUFFER_ADDR:.*]] = alloca i8*, align 8
// CHECK: store i8* %[[BUFFER]], i8** %[[BUFFER_ADDR]], align 8
// CHECK: %[[BUF:.*]] = load i8*, i8** %[[BUFFER_ADDR]], align 8
// CHECK: %[[SUMMARY:.*]] = getelementptr i8, i8* %[[BUF]], i64 0
-// CHECK: store i8 2, i8* %[[SUMMARY]], align 16
+// CHECK: store i8 2, i8* %[[SUMMARY]], align 1
// CHECK: %[[NUMARGS:.*]] = getelementptr i8, i8* %[[BUF]], i64 1
// CHECK: store i8 1, i8* %[[NUMARGS]], align 1
// CHECK: %[[ARGDESCRIPTOR:.*]] = getelementptr i8, i8* %[[BUF]], i64 2
-// CHECK: store i8 96, i8* %[[ARGDESCRIPTOR]], align 2
+// CHECK: store i8 96, i8* %[[ARGDESCRIPTOR]], align 1
// CHECK: %[[ARGSIZE:.*]] = getelementptr i8, i8* %[[BUF]], i64 3
// CHECK: store i8 0, i8* %[[ARGSIZE]], align 1
// CHECK-NEXT: ret void
Index: clang/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- clang/lib/CodeGen/CGBuiltin.cpp
+++ clang/lib/CodeGen/CGBuiltin.cpp
@@ -3594,13 +3594,6 @@
case Builtin::BI__builtin_os_log_format:
return emitBuiltinOSLogFormat(*E);
- case Builtin::BI__builtin_os_log_format_buffer_size: {
- analyze_os_log::OSLogBufferLayout Layout;
- analyze_os_log::computeOSLogBufferLayout(CGM.getContext(), E, Layout);
- return RValue::get(ConstantInt::get(ConvertType(E->getType()),
- Layout.size().getQuantity()));
- }
-
case Builtin::BI__xray_customevent: {
if (!ShouldXRayInstrumentFunction())
return RValue::getIgnored();
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -33,6 +33,7 @@
//
//===----------------------------------------------------------------------===//
+#include "clang/Analysis/Analyses/OSLog.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTDiagnostic.h"
@@ -8112,6 +8113,12 @@
llvm_unreachable("unexpected EvalMode");
}
+ case Builtin::BI__builtin_os_log_format_buffer_size: {
+ analyze_os_log::OSLogBufferLayout Layout;
+ analyze_os_log::computeOSLogBufferLayout(Info.Ctx, E, Layout);
+ return Success(Layout.size().getQuantity(), E);
+ }
+
case Builtin::BI__builtin_bswap16:
case Builtin::BI__builtin_bswap32:
case Builtin::BI__builtin_bswap64: {
Index: clang/test/CodeGen/builtins.c
===================================================================
--- clang/test/CodeGen/builtins.c
+++ clang/test/CodeGen/builtins.c
@@ -729,25 +729,28 @@
// CHECK-LABEL: define void @test_builtin_os_log_errno
void test_builtin_os_log_errno() {
- // CHECK: %[[VLA:.*]] = alloca i8, i64 4, align 16
- // CHECK: call void @__os_log_helper_16_2_1_0_96(i8* %[[VLA]])
+ // CHECK-NOT: @stacksave
+ // CHECK: %[[BUF:.*]] = alloca [4 x i8], align 1
+ // CHECK: %[[DECAY:.*]] = getelementptr inbounds [4 x i8], [4 x i8]* %[[BUF]], i32 0, i32 0
+ // CHECK: call void @__os_log_helper_1_2_1_0_96(i8* %[[DECAY]])
+ // CHECK-NOT: @stackrestore
char buf[__builtin_os_log_format_buffer_size("%m")];
__builtin_os_log_format(buf, "%m");
}
-// CHECK-LABEL: define linkonce_odr hidden void @__os_log_helper_16_2_1_0_96
+// CHECK-LABEL: define linkonce_odr hidden void @__os_log_helper_1_2_1_0_96
// CHECK: (i8* %[[BUFFER:.*]])
// CHECK: %[[BUFFER_ADDR:.*]] = alloca i8*, align 8
// CHECK: store i8* %[[BUFFER]], i8** %[[BUFFER_ADDR]], align 8
// CHECK: %[[BUF:.*]] = load i8*, i8** %[[BUFFER_ADDR]], align 8
// CHECK: %[[SUMMARY:.*]] = getelementptr i8, i8* %[[BUF]], i64 0
-// CHECK: store i8 2, i8* %[[SUMMARY]], align 16
+// CHECK: store i8 2, i8* %[[SUMMARY]], align 1
// CHECK: %[[NUMARGS:.*]] = getelementptr i8, i8* %[[BUF]], i64 1
// CHECK: store i8 1, i8* %[[NUMARGS]], align 1
// CHECK: %[[ARGDESCRIPTOR:.*]] = getelementptr i8, i8* %[[BUF]], i64 2
-// CHECK: store i8 96, i8* %[[ARGDESCRIPTOR]], align 2
+// CHECK: store i8 96, i8* %[[ARGDESCRIPTOR]], align 1
// CHECK: %[[ARGSIZE:.*]] = getelementptr i8, i8* %[[BUF]], i64 3
// CHECK: store i8 0, i8* %[[ARGSIZE]], align 1
// CHECK-NEXT: ret void
Index: clang/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- clang/lib/CodeGen/CGBuiltin.cpp
+++ clang/lib/CodeGen/CGBuiltin.cpp
@@ -3594,13 +3594,6 @@
case Builtin::BI__builtin_os_log_format:
return emitBuiltinOSLogFormat(*E);
- case Builtin::BI__builtin_os_log_format_buffer_size: {
- analyze_os_log::OSLogBufferLayout Layout;
- analyze_os_log::computeOSLogBufferLayout(CGM.getContext(), E, Layout);
- return RValue::get(ConstantInt::get(ConvertType(E->getType()),
- Layout.size().getQuantity()));
- }
-
case Builtin::BI__xray_customevent: {
if (!ShouldXRayInstrumentFunction())
return RValue::getIgnored();
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -33,6 +33,7 @@
//
//===----------------------------------------------------------------------===//
+#include "clang/Analysis/Analyses/OSLog.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTDiagnostic.h"
@@ -8112,6 +8113,12 @@
llvm_unreachable("unexpected EvalMode");
}
+ case Builtin::BI__builtin_os_log_format_buffer_size: {
+ analyze_os_log::OSLogBufferLayout Layout;
+ analyze_os_log::computeOSLogBufferLayout(Info.Ctx, E, Layout);
+ return Success(Layout.size().getQuantity(), E);
+ }
+
case Builtin::BI__builtin_bswap16:
case Builtin::BI__builtin_bswap32:
case Builtin::BI__builtin_bswap64: {
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