Don't attempt to use flags from predicated instructions.
The ARM backend can eliminate cmp instructions by reusing flags from a
nearby sub instruction with similar arguments.
Don't do that if the sub is predicated - the flags are not written
unconditionally.
<rdar://problem/12263428>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163535 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 10c41ee..e2f0d7d 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -2028,13 +2028,14 @@
// Masked compares sometimes use the same register as the corresponding 'and'.
if (CmpMask != ~0) {
- if (!isSuitableForMask(MI, SrcReg, CmpMask, false)) {
+ if (!isSuitableForMask(MI, SrcReg, CmpMask, false) || isPredicated(MI)) {
MI = 0;
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(SrcReg),
UE = MRI->use_end(); UI != UE; ++UI) {
if (UI->getParent() != CmpInstr->getParent()) continue;
MachineInstr *PotentialAND = &*UI;
- if (!isSuitableForMask(PotentialAND, SrcReg, CmpMask, true))
+ if (!isSuitableForMask(PotentialAND, SrcReg, CmpMask, true) ||
+ isPredicated(PotentialAND))
continue;
MI = PotentialAND;
break;
@@ -2100,6 +2101,10 @@
// The single candidate is called MI.
if (!MI) MI = Sub;
+ // We can't use a predicated instruction - it doesn't always write the flags.
+ if (isPredicated(MI))
+ return false;
+
switch (MI->getOpcode()) {
default: break;
case ARM::RSBrr:
@@ -2206,6 +2211,7 @@
// Toggle the optional operand to CPSR.
MI->getOperand(5).setReg(ARM::CPSR);
MI->getOperand(5).setIsDef(true);
+ assert(!isPredicated(MI) && "Can't use flags from predicated instruction");
CmpInstr->eraseFromParent();
// Modify the condition code of operands in OperandsToUpdate.