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c1f65c8564
This is the first commit in a series that add an @llvm.assume intrinsic which can be used to provide the optimizer with a condition it may assume to be true (when the control flow would hit the intrinsic call). Some basic properties are added here: - llvm.invariant(true) is dead. - llvm.invariant(false) is unreachable (this directly corresponds to the documented behavior of MSVC's __assume(0)), so is llvm.invariant(undef). The intrinsic is tagged as writing arbitrarily, in order to maintain control dependencies. BasicAA has been updated, however, to return NoModRef for any particular location-based query so that we don't unnecessarily block code motion. llvm-svn: 213973
23 lines
390 B
LLVM
23 lines
390 B
LLVM
; RUN: opt -simplifycfg -S < %s | FileCheck %s
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define void @test1() {
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call void @llvm.assume(i1 0)
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ret void
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; CHECK-LABEL: @test1
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; CHECK-NOT: llvm.assume
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; CHECK: unreachable
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}
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define void @test2() {
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call void @llvm.assume(i1 undef)
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ret void
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; CHECK-LABEL: @test2
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; CHECK-NOT: llvm.assume
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; CHECK: unreachable
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}
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declare void @llvm.assume(i1) nounwind
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