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Don't generate llvm.expect intrinsics with -O0.

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The backend won't run LowerExpect on -O0.  In a debug LTO build, this results in llvm.expect intrinsics being in the LTO IR which doesn't know how to optimize them.

Thanks to Chandler for the suggestion and review.

Differential revision: http://reviews.llvm.org/D7183

llvm-svn: 227135
This commit is contained in:
Pete Cooper
2015-01-26 20:51:58 +00:00
parent 0dc86722f5
commit f051cbf631
2 changed files with 18 additions and 5 deletions
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7
clang/lib/CodeGen/CGBuiltin.cpp
View File

@@ -389,9 +389,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
Value *ArgValue = EmitScalarExpr(E->getArg(0));
llvm::Type *ArgType = ArgValue->getType();
Value *FnExpect = CGM.getIntrinsic(Intrinsic::expect, ArgType);
Value *ExpectedValue = EmitScalarExpr(E->getArg(1));
// Don't generate llvm.expect on -O0 as the backend won't use it for
// anything.
// Note, we still IRGen ExpectedValue because it could have side-effects.
if (CGM.getCodeGenOpts().OptimizationLevel == 0)
return RValue::get(ArgValue);
Value *FnExpect = CGM.getIntrinsic(Intrinsic::expect, ArgType);
Value *Result = Builder.CreateCall2(FnExpect, ArgValue, ExpectedValue,
"expval");
return RValue::get(Result);

16
clang/test/CodeGen/builtin-expect.c
View File

@@ -1,10 +1,14 @@
// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s -O0 | FileCheck %s --check-prefix=CHECK_O0
int x;
int y(void);
void foo();
void FUNC() {
// CHECK-LABEL: define void @FUNC()
// CHECK: [[call:%.*]] = call i32 @y
// CHECK_O0: [[call:%.*]] = call i32 @y
// CHECK_O0-NOT: call i64 @llvm.expect
if (__builtin_expect (x, y()))
foo ();
}
@@ -17,21 +21,25 @@ int main() {
(void) __builtin_expect((isigprocmask(), 0), bar());
}
// CHECK-LABEL: define i32 @main()
// CHECK: call void @isigprocmask()
// CHECK: [[C:%.*]] = call i64 (...)* @bar()
// CHECK_O0: call void @isigprocmask()
// CHECK_O0: [[C:%.*]] = call i64 (...)* @bar()
// CHECK_O0-NOT: call i64 @llvm.expect
// CHECK: @test1
// CHECK-LABEL: define i32 @test1
int test1(int x) {
// CHECK: @llvm.expect
// CHECK_O0-NOT: call i64 @llvm.expect
if (__builtin_expect (x, 1))
return 0;
return x;
}
// CHECK: @test2
// CHECK: define i32 @test2
int test2(int x) {
// CHECK: @llvm.expect
// CHECK_O0-NOT: call i64 @llvm.expect
switch(__builtin_expect(x, 5)) {
default:
return 0;