[PeepholeOptimizer] Don't assume bitcast def always has input
Summary:
If we have a MI marked with bitcast bits, but without input operands,
PeepholeOptimizer might crash with assert.
eg:
If we apply the changes in PPCInstrVSX.td as in this patch:
[(set v4i32:$XT, (bitconvert (v16i8 immAllOnesV)))]>;
We will get assert in PeepholeOptimizer.
```
llvm-lit llvm-project/llvm/test/CodeGen/PowerPC/build-vector-tests.ll -v
llvm-project/llvm/include/llvm/CodeGen/MachineInstr.h:417: const
llvm::MachineOperand &llvm::MachineInstr::getOperand(unsigned int)
const: Assertion `i < getNumOperands() && "getOperand() out of range!"'
failed.
```
The fix is to abort if we found out of bound access.
Reviewers: qcolombet, MatzeB, hfinkel, arsenm
Reviewed By: qcolombet
Subscribers: wdng, arsenm, steven.zhang, wuzish, nemanjai, hiraditya, kbarton, MaskRay, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D65542
llvm-svn: 369261
diff --git a/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
index e613d07..6818195 100644
--- a/llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -1853,6 +1853,11 @@
SrcIdx = OpIdx;
}
+ // In some rare case, Def has no input, SrcIdx is out of bound,
+ // getOperand(SrcIdx) will fail below.
+ if (SrcIdx >= Def->getNumOperands())
+ return ValueTrackerResult();
+
// Stop when any user of the bitcast is a SUBREG_TO_REG, replacing with a COPY
// will break the assumed guarantees for the upper bits.
for (const MachineInstr &UseMI : MRI.use_nodbg_instructions(DefOp.getReg())) {