[ARM][LowOverheadLoops] Correct offset checking
This patch addresses a couple of problems:
1) The maximum supported offset of LE is -4094.
2) The offset of WLS also needs to be checked, this uses a
maximum positive offset of 4094.
The use of BasicBlockUtils has been changed because the block offsets
weren't being initialised, but the isBBInRange checks both positive
and negative offsets.
ARMISelLowering has been tweaked because the test case presented
another pattern that we weren't supporting.
llvm-svn: 365749
diff --git a/llvm/lib/Target/ARM/ARMBasicBlockInfo.h b/llvm/lib/Target/ARM/ARMBasicBlockInfo.h
index d969a6f..400bba3 100644
--- a/llvm/lib/Target/ARM/ARMBasicBlockInfo.h
+++ b/llvm/lib/Target/ARM/ARMBasicBlockInfo.h
@@ -132,6 +132,10 @@
unsigned getOffsetOf(MachineInstr *MI) const;
+ unsigned getOffsetOf(MachineBasicBlock *MBB) const {
+ return BBInfo[MBB->getNumber()].Offset;
+ }
+
void adjustBBOffsetsAfter(MachineBasicBlock *MBB);
void adjustBBSize(MachineBasicBlock *MBB, int Size) {
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 36b669b..dd11ed6 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -12989,22 +12989,26 @@
const ARMSubtarget *ST) {
// Look for (brcond (xor test.set.loop.iterations, -1)
SDValue CC = N->getOperand(1);
+ unsigned Opc = CC->getOpcode();
+ SDValue Int;
- if (CC->getOpcode() != ISD::XOR && CC->getOpcode() != ISD::SETCC)
+ if ((Opc == ISD::XOR || Opc == ISD::SETCC) &&
+ (CC->getOperand(0)->getOpcode() == ISD::INTRINSIC_W_CHAIN)) {
+
+ assert((isa<ConstantSDNode>(CC->getOperand(1)) &&
+ cast<ConstantSDNode>(CC->getOperand(1))->isOne()) &&
+ "Expected to compare against 1");
+
+ Int = CC->getOperand(0);
+ } else if (CC->getOpcode() == ISD::INTRINSIC_W_CHAIN)
+ Int = CC;
+ else
return SDValue();
- if (CC->getOperand(0)->getOpcode() != ISD::INTRINSIC_W_CHAIN)
- return SDValue();
-
- SDValue Int = CC->getOperand(0);
unsigned IntOp = cast<ConstantSDNode>(Int.getOperand(1))->getZExtValue();
if (IntOp != Intrinsic::test_set_loop_iterations)
return SDValue();
- assert((isa<ConstantSDNode>(CC->getOperand(1)) &&
- cast<ConstantSDNode>(CC->getOperand(1))->isOne()) &&
- "Expected to compare against 1");
-
SDLoc dl(Int);
SDValue Chain = N->getOperand(0);
SDValue Elements = Int.getOperand(2);
diff --git a/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp b/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
index a790ab0..cedf3bd 100644
--- a/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
+++ b/llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
@@ -91,6 +91,7 @@
MF.getSubtarget().getInstrInfo());
BBUtils = std::unique_ptr<ARMBasicBlockUtils>(new ARMBasicBlockUtils(MF));
BBUtils->computeAllBlockSizes();
+ BBUtils->adjustBBOffsetsAfter(&MF.front());
bool Changed = false;
for (auto ML : MLI) {
@@ -200,9 +201,18 @@
End->getOperand(1).getMBB() != ML->getHeader())
report_fatal_error("Expected LoopEnd to target Loop Header");
- // The LE instructions has 12-bits for the label offset.
- if (!BBUtils->isBBInRange(End, ML->getHeader(), 4096)) {
- LLVM_DEBUG(dbgs() << "ARM Loops: Too large for a low-overhead loop!\n");
+ // The WLS and LE instructions have 12-bits for the label offset. WLS
+ // requires a positive offset, while LE uses negative.
+ if (BBUtils->getOffsetOf(End) < BBUtils->getOffsetOf(ML->getHeader()) ||
+ !BBUtils->isBBInRange(End, ML->getHeader(), 4094)) {
+ LLVM_DEBUG(dbgs() << "ARM Loops: LE offset is out-of-range\n");
+ Revert = true;
+ }
+ if (Start->getOpcode() == ARM::t2WhileLoopStart &&
+ (BBUtils->getOffsetOf(Start) >
+ BBUtils->getOffsetOf(Start->getOperand(1).getMBB()) ||
+ !BBUtils->isBBInRange(Start, Start->getOperand(1).getMBB(), 4094))) {
+ LLVM_DEBUG(dbgs() << "ARM Loops: WLS offset is out-of-range!\n");
Revert = true;
}