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5e28cd3473
Summary: Code frequently relies upon the results of "is.constant" intrinsics to DCE invalid code paths. We don't want the intrinsic to be made control- dependent on any additional values. For instance, we can't split a PHI into a "constant" and "non-constant" part via jump threading in order to "optimize" the constant part, because the "is.constant" intrinsic is meant to return "false". Reviewers: wmi, kazu, MaskRay Reviewed By: kazu Subscribers: jdoerfert, efriedma, joerg, lebedev.ri, nikic, xbolva00, hiraditya, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D75799
41 lines
1.2 KiB
LLVM
41 lines
1.2 KiB
LLVM
; RUN: opt -jump-threading -S -verify < %s | FileCheck %s
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; This is reduced from the Linux net/ipv4/tcp.c file built with ASAN. We
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; don't want jump threading to split up a basic block which has a PHI node with
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; at least one constant incoming value, whose value is used by an is.constant
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; intrinsic with non-local uses. It could lead to later passes no DCE'ing
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; invalid paths.
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; CHECK-LABEL: define void @test1(
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; CHECK-LABEL: bb_cond:
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; CHECK-NOT: %sext = phi i64 [ %var, %entry ]
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; CHECK-NEXT: %sext = phi i64 [ 24, %bb_constant ], [ %var, %entry ]
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; CHECK-NEXT: %cond2 = icmp
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; CHECK-NEXT: call i1 @llvm.is.constant.i64(
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define void @test1(i32 %a, i64 %var) {
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entry:
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%cond1 = icmp ugt i32 %a, 24
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br i1 %cond1, label %bb_constant, label %bb_cond
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bb_constant:
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br label %bb_cond
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bb_cond:
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%sext = phi i64 [ 24, %bb_constant ], [ %var, %entry ]
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%cond2 = icmp ugt i64 %sext, 24
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%is_constant = call i1 @llvm.is.constant.i64(i64 %sext)
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br i1 %cond2, label %bb_then, label %bb_else
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bb_then:
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unreachable
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bb_else:
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unreachable
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}
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; Function Attrs: nounwind readnone willreturn
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declare i1 @llvm.is.constant.i64(i64) #0
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attributes #0 = { convergent nounwind readnone willreturn }
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