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99ca015392
Teach LLVM optimize to more precisely in the presence of "deopt" operand bundles. "deopt" operand bundles imply that the call they're attached to is at least `readonly` (i.e. they don't imply clobber semantics), and they don't capture their bundle operands. llvm-svn: 254118
63 lines
1.6 KiB
LLVM
63 lines
1.6 KiB
LLVM
; RUN: opt -S -dse < %s | FileCheck %s
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declare void @f()
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declare noalias i8* @malloc(i32) nounwind
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define void @test_0() {
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; CHECK-LABEL: @test_0(
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%m = call i8* @malloc(i32 24)
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tail call void @f() [ "unknown"(i8* %m) ]
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; CHECK: store i8 -19, i8* %m
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store i8 -19, i8* %m
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ret void
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}
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define i8* @test_1() {
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; CHECK-LABEL: @test_1(
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%m = call i8* @malloc(i32 24)
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tail call void @f() [ "unknown"(i8* %m) ]
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store i8 -19, i8* %m
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tail call void @f()
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store i8 101, i8* %m
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; CHECK: tail call void @f() [ "unknown"(i8* %m) ]
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; CHECK: store i8 -19, i8* %m
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; CHECK: tail call void @f()
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; CHECK: store i8 101, i8* %m
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ret i8* %m
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}
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define void @test_2() {
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; Since the deopt operand bundle does not escape %m (see caveat below), it is
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; legal to elide the final store that location.
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; CHECK-LABEL: @test_2(
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%m = call i8* @malloc(i32 24)
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tail call void @f() [ "deopt"(i8* %m) ]
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store i8 -19, i8* %m
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ret void
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; CHECK: tail call void @f() [ "deopt"(i8* %m) ]
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; CHECK-NEXT ret void
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}
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define i8* @test_3() {
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; Since the deopt operand bundle does not escape %m (see caveat below), @f
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; cannot observe the stores to %m
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; CHECK-LABEL: @test_3(
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%m = call i8* @malloc(i32 24)
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tail call void @f() [ "deopt"(i8* %m) ]
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store i8 -19, i8* %m
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tail call void @f()
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store i8 101, i8* %m
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ret i8* %m
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}
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; Caveat: technically, %m can only escape if the calling function is deoptimized
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; at the call site (i.e. the call returns to the "deopt" continuation). Since
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; the calling function body will be invalidated in that case, the calling
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; function can be optimized under the assumption that %m does not escape.
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