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ConstantFolding: Add a missing folding that leads to a miscompile.

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We use constant folding to see if an intrinsic evaluates to the same value as a
constant that we know. If we don't take the undefinedness into account we get a
value that doesn't match the actual implementation, and miscompiled code.

This was uncovered by Chandler's simplifycfg changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173356 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2013-01-24 16:28:28 +00:00
parent 41d35a335e
commit e574246489
3 changed files with 41 additions and 5 deletions
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36
test/Transforms/InstCombine/intrinsics.ll
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@@ -220,3 +220,39 @@ define i32 @cttz_simplify1b(i32 %x) nounwind readnone ssp {
; CHECK: @cttz_simplify1b
; CHECK-NEXT: ret i32 0
}
define i32 @ctlz_undef(i32 %Value) nounwind {
%ctlz = call i32 @llvm.ctlz.i32(i32 0, i1 true)
ret i32 %ctlz
; CHECK: @ctlz_undef
; CHECK-NEXT: ret i32 undef
}
define i32 @cttz_undef(i32 %Value) nounwind {
%cttz = call i32 @llvm.cttz.i32(i32 0, i1 true)
ret i32 %cttz
; CHECK: @cttz_undef
; CHECK-NEXT: ret i32 undef
}
define i32 @ctlz_select(i32 %Value) nounwind {
%tobool = icmp ne i32 %Value, 0
%ctlz = call i32 @llvm.ctlz.i32(i32 %Value, i1 true)
%s = select i1 %tobool, i32 %ctlz, i32 32
ret i32 %s
; CHECK: @ctlz_select
; CHECK: select i1 %tobool, i32 %ctlz, i32 32
}
define i32 @cttz_select(i32 %Value) nounwind {
%tobool = icmp ne i32 %Value, 0
%cttz = call i32 @llvm.cttz.i32(i32 %Value, i1 true)
%s = select i1 %tobool, i32 %cttz, i32 32
ret i32 %s
; CHECK: @cttz_select
; CHECK: select i1 %tobool, i32 %cttz, i32 32
}