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.
87 lines
4.6 KiB
C++
87 lines
4.6 KiB
C++
// RUN: %clang_cc1 -std=c++11 -triple i686-windows-msvc -emit-llvm %s -o - | FileCheck %s --check-prefix=WINDOWS
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// RUN: %clang_cc1 -std=c++11 -triple x86_64-windows-msvc -emit-llvm %s -o - | FileCheck %s --check-prefix=WINDOWS64
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// RUN: %clang_cc1 -std=c++11 -triple x86_64-pc-linux -emit-llvm %s -o - | FileCheck %s --check-prefix=LINUX
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// RUN: %clang_cc1 -std=c++11 -triple x86_64-apple-macos -emit-llvm %s -o - | FileCheck %s --check-prefix=DARWIN
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struct Foo {
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Foo();
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Foo(const Foo &o);
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~Foo();
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int x;
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};
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int __attribute__((target("default"))) bar(Foo o) { return o.x; }
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int __attribute__((target("sse4.2"))) bar(Foo o) { return o.x + 1; }
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int __attribute__((target("arch=ivybridge"))) bar(Foo o) { return o.x + 2; }
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void usage() {
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Foo f;
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bar(f);
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}
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// DARWIN-NOT: inalloca(
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// LINUX-NOT: inalloca(
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// WINDOWS: define dso_local noundef i32 @"?bar@@YAHUFoo@@@Z"(ptr inalloca(<{ %struct.Foo }>) %0)
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// WINDOWS: %[[O:[0-9a-zA-Z]+]] = getelementptr inbounds nuw <{ %struct.Foo }>, ptr %0, i32 0, i32 0
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// WINDOWS: %[[X:[0-9a-zA-Z]+]] = getelementptr inbounds nuw %struct.Foo, ptr %[[O]], i32 0, i32 0
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// WINDOWS: %[[LOAD:[0-9a-zA-Z]+]] = load i32, ptr %[[X]]
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// WINDOWS: ret i32 %[[LOAD]]
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// WINDOWS: define dso_local noundef i32 @"?bar@@YAHUFoo@@@Z.sse4.2"(ptr inalloca(<{ %struct.Foo }>) %0)
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// WINDOWS: %[[O:[0-9a-zA-Z]+]] = getelementptr inbounds nuw <{ %struct.Foo }>, ptr %0, i32 0, i32 0
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// WINDOWS: %[[X:[0-9a-zA-Z]+]] = getelementptr inbounds nuw %struct.Foo, ptr %[[O]], i32 0, i32 0
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// WINDOWS: %[[LOAD:[0-9a-zA-Z]+]] = load i32, ptr %[[X]]
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// WINDOWS: %[[ADD:[0-9a-zA-Z]+]] = add nsw i32 %[[LOAD]], 1
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// WINDOWS: ret i32 %[[ADD]]
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// WINDOWS: define dso_local noundef i32 @"?bar@@YAHUFoo@@@Z.arch_ivybridge"(ptr inalloca(<{ %struct.Foo }>) %0)
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// WINDOWS: %[[O:[0-9a-zA-Z]+]] = getelementptr inbounds nuw <{ %struct.Foo }>, ptr %0, i32 0, i32 0
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// WINDOWS: %[[X:[0-9a-zA-Z]+]] = getelementptr inbounds nuw %struct.Foo, ptr %[[O]], i32 0, i32 0
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// WINDOWS: %[[LOAD:[0-9a-zA-Z]+]] = load i32, ptr %[[X]]
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// WINDOWS: %[[ADD:[0-9a-zA-Z]+]] = add nsw i32 %[[LOAD]], 2
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// WINDOWS: ret i32 %[[ADD]]
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// WINDOWS: define dso_local void @"?usage@@YAXXZ"()
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// WINDOWS: %[[F:[0-9a-zA-Z]+]] = alloca %struct.Foo
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// WINDOWS: %[[ARGMEM:[0-9a-zA-Z]+]] = alloca inalloca <{ %struct.Foo }>
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// WINDOWS: %[[CALL:[0-9a-zA-Z]+]] = call noundef i32 @"?bar@@YAHUFoo@@@Z.resolver"(ptr inalloca(<{ %struct.Foo }>) %[[ARGMEM]])
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// WINDOWS: define weak_odr dso_local i32 @"?bar@@YAHUFoo@@@Z.resolver"(ptr %0)
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// WINDOWS: %[[RET:[0-9a-zA-Z]+]] = musttail call i32 @"?bar@@YAHUFoo@@@Z.arch_ivybridge"(ptr %0)
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// WINDOWS-NEXT: ret i32 %[[RET]]
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// WINDOWS: %[[RET:[0-9a-zA-Z]+]] = musttail call i32 @"?bar@@YAHUFoo@@@Z.sse4.2"(ptr %0)
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// WINDOWS-NEXT: ret i32 %[[RET]]
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// WINDOWS: %[[RET:[0-9a-zA-Z]+]] = musttail call i32 @"?bar@@YAHUFoo@@@Z"(ptr %0)
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// WINDOWS-NEXT: ret i32 %[[RET]]
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// WINDOWS64: define dso_local noundef i32 @"?bar@@YAHUFoo@@@Z"(ptr dead_on_return noundef %[[O:[0-9a-zA-Z]+]])
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// WINDOWS64: %[[X:[0-9a-zA-Z]+]] = getelementptr inbounds nuw %struct.Foo, ptr %[[O]], i32 0, i32 0
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// WINDOWS64: %[[LOAD:[0-9a-zA-Z]+]] = load i32, ptr %[[X]]
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// WINDOWS64: ret i32 %[[LOAD]]
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// WINDOWS64: define dso_local noundef i32 @"?bar@@YAHUFoo@@@Z.sse4.2"(ptr dead_on_return noundef %[[O:[0-9a-zA-Z]+]])
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// WINDOWS64: %[[X:[0-9a-zA-Z]+]] = getelementptr inbounds nuw %struct.Foo, ptr %[[O]], i32 0, i32 0
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// WINDOWS64: %[[LOAD:[0-9a-zA-Z]+]] = load i32, ptr %[[X]]
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// WINDOWS64: %[[ADD:[0-9a-zA-Z]+]] = add nsw i32 %[[LOAD]], 1
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// WINDOWS64: ret i32 %[[ADD]]
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// WINDOWS64: define dso_local noundef i32 @"?bar@@YAHUFoo@@@Z.arch_ivybridge"(ptr dead_on_return noundef %[[O:[0-9a-zA-Z]+]])
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// WINDOWS64: %[[X:[0-9a-zA-Z]+]] = getelementptr inbounds nuw %struct.Foo, ptr %[[O]], i32 0, i32 0
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// WINDOWS64: %[[LOAD:[0-9a-zA-Z]+]] = load i32, ptr %[[X]]
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// WINDOWS64: %[[ADD:[0-9a-zA-Z]+]] = add nsw i32 %[[LOAD]], 2
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// WINDOWS64: ret i32 %[[ADD]]
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// WINDOWS64: define dso_local void @"?usage@@YAXXZ"()
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// WINDOWS64: %[[F:[0-9a-zA-Z]+]] = alloca %struct.Foo
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// WINDOWS64: %[[ARG:[0-9a-zA-Z.]+]] = alloca %struct.Foo
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// WINDOWS64: %[[CALL:[0-9a-zA-Z]+]] = call noundef i32 @"?bar@@YAHUFoo@@@Z.resolver"(ptr dead_on_return noundef %[[ARG]])
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// WINDOWS64: define weak_odr dso_local i32 @"?bar@@YAHUFoo@@@Z.resolver"(ptr %0)
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// WINDOWS64: %[[RET:[0-9a-zA-Z]+]] = musttail call i32 @"?bar@@YAHUFoo@@@Z.arch_ivybridge"(ptr %0)
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// WINDOWS64-NEXT: ret i32 %[[RET]]
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// WINDOWS64: %[[RET:[0-9a-zA-Z]+]] = musttail call i32 @"?bar@@YAHUFoo@@@Z.sse4.2"(ptr %0)
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// WINDOWS64-NEXT: ret i32 %[[RET]]
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// WINDOWS64: %[[RET:[0-9a-zA-Z]+]] = musttail call i32 @"?bar@@YAHUFoo@@@Z"(ptr %0)
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// WINDOWS64-NEXT: ret i32 %[[RET]]
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