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Pull in r326882 from upstream llvm trunk (by Sjoerd Meijer):

Browse Source 
[ARM] Fix for PR36577

  Don't PerformSHLSimplify if the given node is used by a node that
  also uses a constant because we may get stuck in an infinite combine
  loop.

  bugzilla: https://bugs.llvm.org/show_bug.cgi?id=36577

  Patch by Sam Parker.

  Differential Revision: https://reviews.llvm.org/D44097

This fixes a hang when compiling one particular file in java/openjdk8
for armv6 and armv7.

Reported by:	swills
PR:		226388
This commit is contained in:
dim 2018-03-09 09:21:22 +00:00
parent e35a88be6c
commit 14bd3707e0
1 changed files with 17 additions and 8 deletions
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25
contrib/llvm/lib/Target/ARM/ARMISelLowering.cpp
View File

@ -10201,7 +10201,14 @@ static SDValue PerformSHLSimplify(SDNode *N,
case ISD::XOR:
case ISD::SETCC:
case ARMISD::CMP:
// Check that its not already using a shl.
// Check that the user isn't already using a constant because there
// aren't any instructions that support an immediate operand and a
// shifted operand.
if (isa<ConstantSDNode>(U->getOperand(0)) ||
isa<ConstantSDNode>(U->getOperand(1)))
return SDValue();
// Check that it's not already using a shift.
if (U->getOperand(0).getOpcode() == ISD::SHL ||
U->getOperand(1).getOpcode() == ISD::SHL)
return SDValue();
@ -10223,8 +10230,6 @@ static SDValue PerformSHLSimplify(SDNode *N,
if (!C1ShlC2 || !C2)
return SDValue();
DEBUG(dbgs() << "Trying to simplify shl: "; N->dump());
APInt C2Int = C2->getAPIntValue();
APInt C1Int = C1ShlC2->getAPIntValue();
@ -10238,12 +10243,12 @@ static SDValue PerformSHLSimplify(SDNode *N,
C1Int.lshrInPlace(C2Int);
// The immediates are encoded as an 8-bit value that can be rotated.
unsigned Zeros = C1Int.countLeadingZeros() + C1Int.countTrailingZeros();
if (C1Int.getBitWidth() - Zeros > 8)
return SDValue();
auto LargeImm = [](const APInt &Imm) {
unsigned Zeros = Imm.countLeadingZeros() + Imm.countTrailingZeros();
return Imm.getBitWidth() - Zeros > 8;
};
Zeros = C2Int.countLeadingZeros() + C2Int.countTrailingZeros();
if (C2Int.getBitWidth() - Zeros > 8)
if (LargeImm(C1Int) || LargeImm(C2Int))
return SDValue();
SelectionDAG &DAG = DCI.DAG;
@ -10254,6 +10259,10 @@ static SDValue PerformSHLSimplify(SDNode *N,
// Shift left to compensate for the lshr of C1Int.
SDValue Res = DAG.getNode(ISD::SHL, dl, MVT::i32, BinOp, SHL.getOperand(1));
DEBUG(dbgs() << "Simplify shl use:\n"; SHL.getOperand(0).dump(); SHL.dump();
N->dump());
DEBUG(dbgs() << "Into:\n"; X.dump(); BinOp.dump(); Res.dump());
DAG.ReplaceAllUsesWith(SDValue(N, 0), Res);
return SDValue(N, 0);
}