9e0c06d708
Let Clang emit `dead_on_return` attribute on pointer arguments that are passed indirectly, namely, large aggregates that the ABI mandates be passed by value; thus, the parameter is destroyed within the callee. Writes to such arguments are not observable by the caller after the callee returns. This should desirably enable further MemCpyOpt/DSE optimizations. Previous discussion: https://discourse.llvm.org/t/rfc-add-dead-on-return-attribute/86871.
34 lines
1.1 KiB
C++
34 lines
1.1 KiB
C++
// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -O3 -o - | FileCheck %s
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/// Check that we pass the member pointers indirectly for MinGW64
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// RUN: %clang_cc1 %s -triple=x86_64-windows-gnu -emit-llvm -o - | FileCheck %s -check-prefix MINGW64
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/// We should be able to optimize calls via the indirectly passed member pointers
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// RUN: %clang_cc1 %s -triple=x86_64-windows-gnu -emit-llvm -O3 -o - | FileCheck %s
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struct A {
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virtual int vf1() { return 1; }
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virtual int vf2() { return 2; }
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};
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int f(A* a, int (A::*fp)()) {
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return (a->*fp)();
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}
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// CHECK-LABEL: define{{.*}} i32 @_Z2g1v()
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// CHECK-NOT: }
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// CHECK: ret i32 1
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// MINGW64-LABEL: define dso_local noundef i32 @_Z2g1v()
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// MINGW64: call noundef i32 @_Z1fP1AMS_FivE(ptr noundef %{{.*}}, ptr dead_on_return noundef %{{.*}})
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int g1() {
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A a;
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return f(&a, &A::vf1);
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}
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// CHECK-LABEL: define{{.*}} i32 @_Z2g2v()
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// CHECK-NOT: }
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// CHECK: ret i32 2
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// MINGW64-LABEL: define dso_local noundef i32 @_Z2g2v()
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// MINGW64: call noundef i32 @_Z1fP1AMS_FivE(ptr noundef %{{.*}}, ptr dead_on_return noundef %{{.*}})
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int g2() {
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A a;
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return f(&a, &A::vf2);
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}
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