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.
79 lines
3.4 KiB
C++
79 lines
3.4 KiB
C++
// RUN: %clang_cc1 -w -triple i686-pc-win32 -emit-llvm -o - %s | FileCheck %s
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// PR44395
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// MSVC passes up to three vectors in registers, and the rest indirectly. Check
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// that both are compatible with an inalloca prototype.
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struct NonTrivial {
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NonTrivial();
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NonTrivial(const NonTrivial &o);
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unsigned handle;
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};
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typedef float __m128 __attribute__((__vector_size__(16), __aligned__(16)));
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__m128 gv128;
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// nt, w, and q will be in the inalloca pack.
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void receive_vec_128(NonTrivial nt, __m128 x, __m128 y, __m128 z, __m128 w, __m128 q) {
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gv128 = x + y + z + w + q;
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}
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// CHECK-LABEL: define dso_local void @"?receive_vec_128@@YAXUNonTrivial@@T__m128@@1111@Z"
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// CHECK-SAME: (<4 x float> inreg noundef %x,
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// CHECK-SAME: <4 x float> inreg noundef %y,
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// CHECK-SAME: <4 x float> inreg noundef %z,
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// CHECK-SAME: ptr inalloca(<{ %struct.NonTrivial, ptr, ptr }>) %0)
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void pass_vec_128() {
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__m128 z = {0};
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receive_vec_128(NonTrivial(), z, z, z, z, z);
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}
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// CHECK-LABEL: define dso_local void @"?pass_vec_128@@YAXXZ"()
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// CHECK: getelementptr inbounds nuw <{ %struct.NonTrivial, ptr, ptr }>, ptr %{{[^,]*}}, i32 0, i32 0
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// CHECK: call x86_thiscallcc noundef ptr @"??0NonTrivial@@QAE@XZ"(ptr {{[^,]*}} %{{.*}})
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// Store q, store temp alloca.
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// CHECK: store <4 x float> %{{[^,]*}}, ptr %{{[^,]*}}, align 16
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// CHECK: getelementptr inbounds nuw <{ %struct.NonTrivial, ptr, ptr }>, ptr %{{[^,]*}}, i32 0, i32 1
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// CHECK: store ptr %{{[^,]*}}, ptr %{{[^,]*}}, align 4
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// Store w, store temp alloca.
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// CHECK: store <4 x float> %{{[^,]*}}, ptr %{{[^,]*}}, align 16
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// CHECK: getelementptr inbounds nuw <{ %struct.NonTrivial, ptr, ptr }>, ptr %{{[^,]*}}, i32 0, i32 2
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// CHECK: store ptr %{{[^,]*}}, ptr %{{[^,]*}}, align 4
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// CHECK: call void @"?receive_vec_128@@YAXUNonTrivial@@T__m128@@1111@Z"
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// CHECK-SAME: (<4 x float> inreg noundef %{{[^,]*}},
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// CHECK-SAME: <4 x float> inreg noundef %{{[^,]*}},
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// CHECK-SAME: <4 x float> inreg noundef %{{[^,]*}},
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// CHECK-SAME: ptr inalloca(<{ %struct.NonTrivial, ptr, ptr }>) %{{[^,]*}})
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// w will be passed indirectly by register, and q will be passed indirectly, but
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// the pointer will be in memory.
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void __fastcall fastcall_receive_vec(__m128 x, __m128 y, __m128 z, __m128 w, int edx, __m128 q, NonTrivial nt) {
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gv128 = x + y + z + w + q;
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}
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// CHECK-LABEL: define dso_local x86_fastcallcc void @"?fastcall_receive_vec@@Y{{[^"]*}}"
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// CHECK-SAME: (<4 x float> inreg noundef %x,
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// CHECK-SAME: <4 x float> inreg noundef %y,
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// CHECK-SAME: <4 x float> inreg noundef %z,
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// CHECK-SAME: ptr dead_on_return inreg noundef %0,
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// CHECK-SAME: i32 inreg noundef %edx,
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// CHECK-SAME: ptr inalloca(<{ ptr, %struct.NonTrivial }>) %1)
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void __vectorcall vectorcall_receive_vec(double xmm0, double xmm1, double xmm2,
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__m128 x, __m128 y, __m128 z,
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__m128 w, int edx, __m128 q, NonTrivial nt) {
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gv128 = x + y + z + w + q;
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}
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// CHECK-LABEL: define dso_local x86_vectorcallcc void @"?vectorcall_receive_vec@@Y{{[^"]*}}"
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// CHECK-SAME: (double inreg noundef %xmm0,
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// CHECK-SAME: double inreg noundef %xmm1,
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// CHECK-SAME: double inreg noundef %xmm2,
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// CHECK-SAME: <4 x float> inreg noundef %x,
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// CHECK-SAME: <4 x float> inreg noundef %y,
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// CHECK-SAME: <4 x float> inreg noundef %z,
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// CHECK-SAME: ptr dead_on_return inreg noundef %0,
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// CHECK-SAME: i32 inreg noundef %edx,
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// CHECK-SAME: ptr inalloca(<{ ptr, %struct.NonTrivial }>) %1)
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