
This patch canonicalizes getelementptr instructions with constant indices to use the `i8` source element type. This makes it easier for optimizations to recognize that two GEPs are identical, because they don't need to see past many different ways to express the same offset. This is a first step towards https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699. This is limited to constant GEPs only for now, as they have a clear canonical form, while we're not yet sure how exactly to deal with variable indices. The test llvm/test/Transforms/PhaseOrdering/switch_with_geps.ll gives two representative examples of the kind of optimization improvement we expect from this change. In the first test SimplifyCFG can now realize that all switch branches are actually the same. In the second test it can convert it into simple arithmetic. These are representative of common optimization failures we see in Rust. Fixes https://github.com/llvm/llvm-project/issues/69841.
122 lines
6.1 KiB
C++
122 lines
6.1 KiB
C++
// RUN: %clang_cc1 -emit-llvm -O1 -o - -fexceptions -triple=i386-pc-win32 %s | FileCheck %s
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struct S { char a; };
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struct V { virtual void f(); };
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struct A : virtual V {};
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struct B : S, virtual V {};
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struct T {};
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T* test0() { return dynamic_cast<T*>((B*)0); }
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// CHECK-LABEL: define dso_local noalias noundef ptr @"?test0@@YAPAUT@@XZ"()
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// CHECK: ret ptr null
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T* test1(V* x) { return &dynamic_cast<T&>(*x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test1@@YAPAUT@@PAUV@@@Z"(ptr noundef %x)
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// CHECK: [[CALL:%.*]] = tail call ptr @__RTDynamicCast(ptr %x, i32 0, ptr nonnull @"??_R0?AUV@@@8", ptr nonnull @"??_R0?AUT@@@8", i32 1)
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// CHECK-NEXT: ret ptr [[CALL]]
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T* test2(A* x) { return &dynamic_cast<T&>(*x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test2@@YAPAUT@@PAUA@@@Z"(ptr noundef %x)
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// CHECK: [[VBTBL:%.*]] = load ptr, ptr %x, align 4
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// CHECK-NEXT: [[VBOFFP:%.*]] = getelementptr inbounds i8, ptr [[VBTBL]], i32 4
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// CHECK-NEXT: [[VBOFFS:%.*]] = load i32, ptr [[VBOFFP]], align 4
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// CHECK-NEXT: [[ADJ:%.*]] = getelementptr inbounds i8, ptr %x, i32 [[VBOFFS]]
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// CHECK-NEXT: [[CALL:%.*]] = tail call ptr @__RTDynamicCast(ptr nonnull [[ADJ]], i32 [[VBOFFS]], ptr nonnull @"??_R0?AUA@@@8", ptr nonnull @"??_R0?AUT@@@8", i32 1)
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// CHECK-NEXT: ret ptr [[CALL]]
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T* test3(B* x) { return &dynamic_cast<T&>(*x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test3@@YAPAUT@@PAUB@@@Z"(ptr noundef %x)
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// CHECK: [[VBPTR:%.*]] = getelementptr inbounds i8, ptr %x, i32 4
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// CHECK-NEXT: [[VBTBL:%.*]] = load ptr, ptr [[VBPTR:%.*]], align 4
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// CHECK-NEXT: [[VBOFFP:%.*]] = getelementptr inbounds i8, ptr [[VBTBL]], i32 4
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// CHECK-NEXT: [[VBOFFS:%.*]] = load i32, ptr [[VBOFFP]], align 4
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// CHECK-NEXT: [[DELTA:%.*]] = add nsw i32 [[VBOFFS]], 4
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// CHECK-NEXT: [[ADJ:%.*]] = getelementptr inbounds i8, ptr %x, i32 [[DELTA]]
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// CHECK-NEXT: [[CALL:%.*]] = tail call ptr @__RTDynamicCast(ptr [[ADJ]], i32 [[DELTA]], ptr nonnull @"??_R0?AUB@@@8", ptr nonnull @"??_R0?AUT@@@8", i32 1)
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// CHECK-NEXT: ret ptr [[CALL]]
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T* test4(V* x) { return dynamic_cast<T*>(x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test4@@YAPAUT@@PAUV@@@Z"(ptr noundef %x)
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// CHECK: [[CALL:%.*]] = tail call ptr @__RTDynamicCast(ptr %x, i32 0, ptr nonnull @"??_R0?AUV@@@8", ptr nonnull @"??_R0?AUT@@@8", i32 0)
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// CHECK-NEXT: ret ptr [[CALL]]
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T* test5(A* x) { return dynamic_cast<T*>(x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test5@@YAPAUT@@PAUA@@@Z"(ptr noundef %x)
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// CHECK: [[CHECK:%.*]] = icmp eq ptr %x, null
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// CHECK-NEXT: br i1 [[CHECK]]
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// CHECK: [[VBTBL:%.*]] = load ptr, ptr %x, align 4
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// CHECK-NEXT: [[VBOFFP:%.*]] = getelementptr inbounds i8, ptr [[VBTBL]], i32 4
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// CHECK-NEXT: [[VBOFFS:%.*]] = load i32, ptr [[VBOFFP]], align 4
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// CHECK-NEXT: [[ADJ:%.*]] = getelementptr inbounds i8, ptr %x, i32 [[VBOFFS]]
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// CHECK-NEXT: [[CALL:%.*]] = tail call ptr @__RTDynamicCast(ptr nonnull [[ADJ]], i32 [[VBOFFS]], ptr {{.*}}@"??_R0?AUA@@@8", ptr {{.*}}@"??_R0?AUT@@@8", i32 0)
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// CHECK-NEXT: br label
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// CHECK: [[RET:%.*]] = phi ptr
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// CHECK-NEXT: ret ptr [[RET]]
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T* test6(B* x) { return dynamic_cast<T*>(x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test6@@YAPAUT@@PAUB@@@Z"(ptr noundef %x)
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// CHECK: [[CHECK:%.*]] = icmp eq ptr %x, null
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// CHECK-NEXT: br i1 [[CHECK]]
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// CHECK: [[VBPTR:%.*]] = getelementptr inbounds i8, ptr %x, i32 4
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// CHECK-NEXT: [[VBTBL:%.*]] = load ptr, ptr [[VBPTR]], align 4
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// CHECK-NEXT: [[VBOFFP:%.*]] = getelementptr inbounds i8, ptr [[VBTBL]], i32 4
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// CHECK-NEXT: [[VBOFFS:%.*]] = load i32, ptr [[VBOFFP]], align 4
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// CHECK-NEXT: [[DELTA:%.*]] = add nsw i32 [[VBOFFS]], 4
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// CHECK-NEXT: [[ADJ:%.*]] = getelementptr inbounds i8, ptr %x, i32 [[DELTA]]
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// CHECK-NEXT: [[CALL:%.*]] = tail call ptr @__RTDynamicCast(ptr nonnull [[ADJ]], i32 [[DELTA]], ptr {{.*}}@"??_R0?AUB@@@8", ptr {{.*}}@"??_R0?AUT@@@8", i32 0)
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// CHECK-NEXT: br label
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// CHECK: [[RET:%.*]] = phi ptr
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// CHECK-NEXT: ret ptr [[RET]]
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void* test7(V* x) { return dynamic_cast<void*>(x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test7@@YAPAXPAUV@@@Z"(ptr noundef %x)
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// CHECK: [[RET:%.*]] = tail call ptr @__RTCastToVoid(ptr %x)
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// CHECK-NEXT: ret ptr [[RET]]
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void* test8(A* x) { return dynamic_cast<void*>(x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test8@@YAPAXPAUA@@@Z"(ptr noundef %x)
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// CHECK: [[CHECK:%.*]] = icmp eq ptr %x, null
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// CHECK-NEXT: br i1 [[CHECK]]
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// CHECK: [[VBTBL:%.*]] = load ptr, ptr %x, align 4
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// CHECK-NEXT: [[VBOFFP:%.*]] = getelementptr inbounds i8, ptr [[VBTBL]], i32 4
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// CHECK-NEXT: [[VBOFFS:%.*]] = load i32, ptr [[VBOFFP]], align 4
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// CHECK-NEXT: [[ADJ:%.*]] = getelementptr inbounds i8, ptr %x, i32 [[VBOFFS]]
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// CHECK-NEXT: [[RES:%.*]] = tail call ptr @__RTCastToVoid(ptr nonnull [[ADJ]])
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// CHECK-NEXT: br label
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// CHECK: [[RET:%.*]] = phi ptr
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// CHECK-NEXT: ret ptr [[RET]]
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void* test9(B* x) { return dynamic_cast<void*>(x); }
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// CHECK-LABEL: define dso_local noundef ptr @"?test9@@YAPAXPAUB@@@Z"(ptr noundef %x)
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// CHECK: [[CHECK:%.*]] = icmp eq ptr %x, null
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// CHECK-NEXT: br i1 [[CHECK]]
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// CHECK: [[VBPTR:%.*]] = getelementptr inbounds i8, ptr %x, i32 4
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// CHECK-NEXT: [[VBTBL:%.*]] = load ptr, ptr [[VBPTR]], align 4
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// CHECK-NEXT: [[VBOFFP:%.*]] = getelementptr inbounds i8, ptr [[VBTBL]], i32 4
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// CHECK-NEXT: [[VBOFFS:%.*]] = load i32, ptr [[VBOFFP]], align 4
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// CHECK-NEXT: [[BASE:%.*]] = getelementptr i8, ptr %x, i32 [[VBOFFS]]
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// CHECK-NEXT: [[ADJ:%.*]] = getelementptr i8, ptr [[BASE]], i32 4
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// CHECK-NEXT: [[CALL:%.*]] = tail call ptr @__RTCastToVoid(ptr [[ADJ]])
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// CHECK-NEXT: br label
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// CHECK: [[RET:%.*]] = phi ptr
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// CHECK-NEXT: ret ptr [[RET]]
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namespace PR25606 {
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struct Cleanup {
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~Cleanup();
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};
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struct S1 { virtual ~S1(); };
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struct S2 : virtual S1 {};
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struct S3 : S2 {};
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S3 *f(S2 &s) {
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Cleanup c;
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return dynamic_cast<S3 *>(&s);
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}
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// CHECK-LABEL: define dso_local noundef ptr @"?f@PR25606@@YAPAUS3@1@AAUS2@1@@Z"(
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// CHECK: [[CALL:%.*]] = invoke ptr @__RTDynamicCast
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// CHECK: call x86_thiscallcc void @"??1Cleanup@PR25606@@QAE@XZ"(
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// CHECK: ret ptr [[CALL]]
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}
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