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[DAGCombiner] extractShiftForRotate - fix out of range shift issue

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Don't just check for negative shift amounts.

Fixes OSS Fuzz #9935
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9935

llvm-svn: 340015
This commit is contained in:
Simon Pilgrim 2018-08-17 12:25:18 +00:00
parent d4d067ef1f
commit cf9b1ab137
2 changed files with 15 additions and 2 deletions
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4
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -5276,9 +5276,9 @@ static SDValue extractShiftForRotate(SelectionDAG &DAG, SDValue OppShift,
// Compute the shift amount we need to extract to complete the rotate.
const unsigned VTWidth = ShiftedVT.getScalarSizeInBits();
APInt NeededShiftAmt = VTWidth - OppShiftCst->getAPIntValue();
if (NeededShiftAmt.isNegative())
if (OppShiftCst->getAPIntValue().ugt(VTWidth))
return SDValue();
APInt NeededShiftAmt = VTWidth - OppShiftCst->getAPIntValue();
// Normalize the bitwidth of the two mul/udiv/shift constant operands.
APInt ExtractFromAmt = ExtractFromCst->getAPIntValue();
APInt OppLHSAmt = OppLHSCst->getAPIntValue();

13
test/CodeGen/X86/combine-rotates.ll
View File

@ -341,3 +341,16 @@ define <4 x i32> @rotate_demanded_bits_3(<4 x i32>, <4 x i32>) {
%9 = or <4 x i32> %5, %8
ret <4 x i32> %9
}
; OSS Fuzz: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9935
define i32 @fuzz9935() {
; CHECK-LABEL: fuzz9935:
; CHECK: # %bb.0:
; CHECK-NEXT: movl $-1, %eax
; CHECK-NEXT: retq
%1 = trunc i40 549755813887 to i32
%2 = mul i32 %1, %1
%3 = lshr i32 %2, %1
%4 = or i32 %3, %2
ret i32 %4
}