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[SystemZ] Validate shifted compare value in adjustForTestUnderMask

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When folding a shift into a test-under-mask comparison, make sure that
there is no loss of precision when creating the shifted comparison
value.  This usually never happens, except for certain always-true
comparisons in unoptimized code.

Fixes PR35529.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319818 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ulrich Weigand 2017-12-05 19:42:07 +00:00
parent 952471eaa5
commit b7cbf75ecd
2 changed files with 24 additions and 0 deletions
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2
lib/Target/SystemZ/SystemZISelLowering.cpp
View File

@ -2201,6 +2201,7 @@ static void adjustForTestUnderMask(SelectionDAG &DAG, const SDLoc &DL,
NewC.Op0.getOpcode() == ISD::SHL &&
isSimpleShift(NewC.Op0, ShiftVal) &&
(MaskVal >> ShiftVal != 0) &&
((CmpVal >> ShiftVal) << ShiftVal) == CmpVal &&
(NewCCMask = getTestUnderMaskCond(BitSize, NewC.CCMask,
MaskVal >> ShiftVal,
CmpVal >> ShiftVal,
@ -2211,6 +2212,7 @@ static void adjustForTestUnderMask(SelectionDAG &DAG, const SDLoc &DL,
NewC.Op0.getOpcode() == ISD::SRL &&
isSimpleShift(NewC.Op0, ShiftVal) &&
(MaskVal << ShiftVal != 0) &&
((CmpVal << ShiftVal) >> ShiftVal) == CmpVal &&
(NewCCMask = getTestUnderMaskCond(BitSize, NewC.CCMask,
MaskVal << ShiftVal,
CmpVal << ShiftVal,

22
test/CodeGen/SystemZ/int-cmp-47.ll
View File

@ -342,3 +342,25 @@ store:
exit:
ret void
}
; Check that we don't fold a shift if the comparison value
; would need to be shifted out of range
define void @f19(i64 %a) {
; CHECK-LABEL: f19:
; CHECK-NOT: tmhh
; CHECK: srlg [[REG:%r[0-5]]], %r2, 63
; CHECK: cgibl [[REG]], 3, 0(%r14)
; CHECK: br %r14
entry:
%shr = lshr i64 %a, 63
%cmp = icmp ult i64 %shr, 3
br i1 %cmp, label %exit, label %store
store:
store i32 1, i32 *@g
br label %exit
exit:
ret void
}