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.
21 lines
459 B
C++
21 lines
459 B
C++
// RUN: %clang_cc1 %s -triple=arm-unknown-linux-gnueabi -target-abi aapcs -emit-llvm -o - | FileCheck %s
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class SMLoc {
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const char *Ptr;
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public:
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SMLoc();
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SMLoc(const SMLoc &RHS);
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};
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SMLoc foo(void *p);
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void bar(void *x) {
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foo(x);
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}
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void zed(SMLoc x);
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void baz() {
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SMLoc a;
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zed(a);
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}
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// CHECK: declare void @_Z3fooPv(ptr dead_on_unwind writable sret(%class.SMLoc) align 4, ptr noundef)
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// CHECK: declare void @_Z3zed5SMLoc(ptr dead_on_return noundef)
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