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llvm-project/llvm/test/Transforms/SimplifyCFG/assume.ll

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Add @llvm.assume, lowering, and some basic properties 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
2014-07-26 05:13:35 +08:00
; RUN: opt -simplifycfg -S < %s | FileCheck %s
define void @test1() {
call void @llvm.assume(i1 0)
ret void
; CHECK-LABEL: @test1
; CHECK-NOT: llvm.assume
; CHECK: unreachable
}
define void @test2() {
call void @llvm.assume(i1 undef)
ret void
; CHECK-LABEL: @test2
; CHECK-NOT: llvm.assume
; CHECK: unreachable
}
declare void @llvm.assume(i1) nounwind