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Fix PR16360

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When (srl (anyextend x), c) is folded into (anyextend (srl x, c)), the
high bits are not cleared. Add 'and' to clear off them.

llvm-svn: 184575
This commit is contained in:
Michael Liao 2013-06-21 18:45:27 +00:00
parent 777b242083
commit cc3b61f064
2 changed files with 21 additions and 3 deletions
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8
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -3915,8 +3915,7 @@ SDValue DAGCombiner::visitSRL(SDNode *N) {
DAG.getConstant(~0ULL >> ShAmt, VT));
}
// fold (srl (anyextend x), c) -> (anyextend (srl x, c))
// fold (srl (anyextend x), c) -> (and (anyextend (srl x, c)), mask)
if (N1C && N0.getOpcode() == ISD::ANY_EXTEND) {
// Shifting in all undef bits?
EVT SmallVT = N0.getOperand(0).getValueType();
@ -3929,7 +3928,10 @@ SDValue DAGCombiner::visitSRL(SDNode *N) {
N0.getOperand(0),
DAG.getConstant(ShiftAmt, getShiftAmountTy(SmallVT)));
AddToWorkList(SmallShift.getNode());
return DAG.getNode(ISD::ANY_EXTEND, SDLoc(N), VT, SmallShift);
APInt Mask = APInt::getAllOnesValue(VT.getSizeInBits()).lshr(ShiftAmt);
return DAG.getNode(ISD::AND, SDLoc(N), VT,
DAG.getNode(ISD::ANY_EXTEND, SDLoc(N), VT, SmallShift),
DAG.getConstant(Mask, VT));
}
}

16
test/CodeGen/X86/pr16360.ll Normal file
View File

@ -0,0 +1,16 @@
; RUN: llc < %s -mtriple=i686-pc-linux | FileCheck %s
define i64 @foo(i32 %sum) {
entry:
%conv = sext i32 %sum to i64
%shr = lshr i64 %conv, 2
%or = or i64 4611686018360279040, %shr
ret i64 %or
}
; CHECK: foo
; CHECK: shrl $2
; CHECK: orl $-67108864
; CHECK-NOT: movl $-1
; CHECK: movl $1073741823
; CHECK: ret