7abefc4222
The motivation for this is that while both memcpyopt and dse will catch this case, both are limited by MSSA's walk back threshold when finding clobbers. As such, if you have a memcpy of an otherwise dead alloca placed towards the end of a long basic block with lots of other memory instructions, it would be missed. This is a bit undesirable for such an "obviously" useless bit of code. As noted in comments, we should probably generalize instcombine's escape analysis peephole (see visitAllocInst) to allow read xor write. Doing that would subsume this code in a more general way, but is also a more involved change. For the moment, I went with the easiest fix.
106 lines
3.8 KiB
LLVM
106 lines
3.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -basic-aa -tailcallelim -inline -instcombine -dse -S | FileCheck %s
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; RUN: opt < %s -aa-pipeline=basic-aa -passes='function(tailcallelim),cgscc(inline,function(instcombine,dse))' -S | FileCheck %s
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; PR7272
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; Calls that capture byval parameters cannot be marked as tail calls. Other
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; tails that don't capture byval parameters can still be tail calls.
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target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32"
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target triple = "i386-pc-linux-gnu"
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declare void @ext(i32*)
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define void @bar(i32* byval(i32) %x) {
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; CHECK-LABEL: @bar(
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; CHECK-NEXT: call void @ext(i32* nonnull [[X:%.*]])
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; CHECK-NEXT: ret void
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;
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call void @ext(i32* %x)
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ret void
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}
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define void @foo(i32* %x) {
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; CHECK-LABEL: @foo(
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; CHECK-NEXT: [[X1:%.*]] = alloca i32, align 4
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; CHECK-NEXT: [[TMP1:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[TMP1]])
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; CHECK-NEXT: [[TMP2:%.*]] = load i32, i32* [[X:%.*]], align 1
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; CHECK-NEXT: store i32 [[TMP2]], i32* [[X1]], align 4
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; CHECK-NEXT: call void @ext(i32* nonnull [[X1]])
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; CHECK-NEXT: [[TMP3:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[TMP3]])
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; CHECK-NEXT: ret void
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;
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call void @bar(i32* byval(i32) %x)
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ret void
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}
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define internal void @qux(i32* byval(i32) %x) {
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call void @ext(i32* %x)
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tail call void @ext(i32* null)
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ret void
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}
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define void @frob(i32* %x) {
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; CHECK-LABEL: @frob(
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; CHECK-NEXT: [[X1:%.*]] = alloca i32, align 4
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; CHECK-NEXT: [[TMP1:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[TMP1]])
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; CHECK-NEXT: [[TMP2:%.*]] = load i32, i32* [[X:%.*]], align 1
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; CHECK-NEXT: store i32 [[TMP2]], i32* [[X1]], align 4
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; CHECK-NEXT: call void @ext(i32* nonnull [[X1]])
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; CHECK-NEXT: tail call void @ext(i32* null)
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; CHECK-NEXT: [[TMP3:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[TMP3]])
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; CHECK-NEXT: ret void
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;
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tail call void @qux(i32* byval(i32) %x)
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ret void
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}
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; A byval parameter passed into a function which is passed out as byval does
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; not block the call from being marked as tail.
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declare void @ext2(i32* byval(i32))
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define void @bar2(i32* byval(i32) %x) {
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; CHECK-LABEL: @bar2(
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; CHECK-NEXT: tail call void @ext2(i32* nonnull byval(i32) [[X:%.*]])
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; CHECK-NEXT: ret void
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;
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call void @ext2(i32* byval(i32) %x)
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ret void
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}
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define void @foobar(i32* %x) {
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; CHECK-LABEL: @foobar(
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; CHECK-NEXT: [[X1:%.*]] = alloca i32, align 4
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; CHECK-NEXT: [[TMP1:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[TMP1]])
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; CHECK-NEXT: [[TMP2:%.*]] = load i32, i32* [[X:%.*]], align 1
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; CHECK-NEXT: store i32 [[TMP2]], i32* [[X1]], align 4
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; CHECK-NEXT: tail call void @ext2(i32* nonnull byval(i32) [[X1]])
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; CHECK-NEXT: [[TMP3:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[TMP3]])
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; CHECK-NEXT: ret void
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;
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tail call void @bar2(i32* byval(i32) %x)
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ret void
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}
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define void @barfoo() {
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; CHECK-LABEL: @barfoo(
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; CHECK-NEXT: [[X1:%.*]] = alloca i32, align 4
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; CHECK-NEXT: [[TMP1:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[TMP1]])
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; CHECK-NEXT: tail call void @ext2(i32* nonnull byval(i32) [[X1]])
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; CHECK-NEXT: [[TMP2:%.*]] = bitcast i32* [[X1]] to i8*
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; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[TMP2]])
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; CHECK-NEXT: ret void
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;
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%x = alloca i32
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tail call void @bar2(i32* byval(i32) %x)
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ret void
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}
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