e2d7cd685d
This patch makes the dead_on_return parameter attribute optionally require a number
of bytes to be passed in to specify the number of bytes known to be dead
upon function return/unwind. This is aimed at enabling annotating the
this pointer in C++ destructors with dead_on_return in clang. We need
this to handle cases like the following:
```
struct X {
int n;
~X() {
this[n].n = 0;
}
};
void f() {
X xs[] = {42, -1};
}
```
Where we only certain that sizeof(X) bytes are dead upon return of ~X.
Otherwise DSE would be able to eliminate the store in ~X which would not
be correct.
This patch only does the wiring within IR. Future patches will make
clang emit correct sizing information and update DSE to only delete
stores to objects marked dead_on_return that are provably in bounds of
the number of bytes specified to be dead_on_return.
Reviewers: nikic, alinas, antoniofrighetto
Pull Request: https://github.com/llvm/llvm-project/pull/171712
64 lines
2.2 KiB
C++
64 lines
2.2 KiB
C++
// RUN: %clang_cc1 -triple i686-windows-msvc -emit-llvm -o - %s 2>&1 | FileCheck %s
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struct A {
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A();
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A(const A &);
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int x;
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};
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void decayToFp(int (*f)(A));
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void test() {
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auto ld = [](A a) {
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static int calls = 0;
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++calls;
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return a.x + calls;
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};
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decayToFp(ld);
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ld(A{});
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}
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// CHECK: define internal x86_thiscallcc noundef i32
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// CHECK-SAME: @"??R<lambda_0>@?0??test@@YAXXZ@QBE?A?<auto>@@UA@@@Z"
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// CHECK-SAME: (ptr noundef %this, ptr inalloca(<{ %struct.A }>) %[[ARG:.*]])
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// CHECK: %[[V:.*]] = getelementptr inbounds nuw <{ %struct.A }>, ptr %[[ARG]], i32 0, i32 0
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// CHECK: %call = call x86_thiscallcc noundef i32
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// CHECK-SAME: @"?__impl@<lambda_0>@?0??test@@YAXXZ@QBE?A?<auto>@@UA@@@Z"
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// CHECK-SAME: (ptr noundef %this, ptr noundef dead_on_return %[[V]])
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// CHECK: define internal noundef i32
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// CHECK-SAME: @"?__invoke@<lambda_0>@?0??test@@YAXXZ@CA?A?<auto>@@UA@@@Z"
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// CHECK-SAME: (ptr inalloca(<{ %struct.A }>) %[[ARG:.*]])
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// CHECK: %unused.capture = alloca %class.anon, align 1
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// CHECK: %[[VAR:.*]] = getelementptr inbounds nuw <{ %struct.A }>, ptr %[[ARG]], i32 0, i32 0
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// CHECK: %call = call x86_thiscallcc noundef i32
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// CHECK-SAME: @"?__impl@<lambda_0>@?0??test@@YAXXZ@QBE?A?<auto>@@UA@@@Z"
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// CHECK-SAME: (ptr noundef %unused.capture, ptr noundef dead_on_return %[[VAR]])
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// CHECK: ret i32 %call
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// CHECK: define internal x86_thiscallcc noundef i32
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// CHECK-SAME: @"?__impl@<lambda_0>@?0??test@@YAXXZ@QBE?A?<auto>@@UA@@@Z"
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// CHECK-SAME: (ptr noundef %this, ptr noundef dead_on_return %[[ARG:.*]])
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// CHECK: %this.addr = alloca ptr, align 4
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// CHECK: store ptr %this, ptr %this.addr, align 4
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// CHECK: %this1 = load ptr, ptr %this.addr, align 4
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// CHECK: %{{.*}} = load i32, ptr @"?calls@?1???R<lambda_0>
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// CHECK: %inc = add nsw i32 %{{.*}}, 1
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// CHECK: store i32 %inc, ptr @"?calls@?1???R<lambda_0>
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// CHECK: %{{.*}} = getelementptr inbounds nuw %struct.A, ptr %{{.*}}, i32 0, i32 0
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// CHECK: %{{.*}} = load i32, ptr %{{.*}}, align 4
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// CHECK: %{{.*}} = load i32, ptr @"?calls@?1???R<lambda_0>
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// CHECK: %add = add nsw i32 %{{.*}}, %{{.*}}
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// CHECK: ret i32 %add
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// Make sure we don't try to copy an uncopyable type.
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struct B {
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B();
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B(B &);
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void operator=(B);
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long long x;
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} b;
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void f() {
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[](B) {}(b);
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}
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