[RISCV] Node returned by foldBinOpIntoSelectIfProfitable reports error in lowerSELECT

[Yunzezhu94]

Here is a simple reduced case:
int a = (a ? 4 : 8) / (8 ? -5141143369814759789L : 0);
When compiling this case with order
clang++ -std=c++11 -march=rv64imafdc -mabi=lp64d -w -O0 -o a.o -c a.cpp
It reports error: llvm-project/llvm/include/llvm/CodeGen/SelectionDAGNodes.h:960: const llvm::SDValue& llvm::SDNode::getOperand(unsigned int) const: Assertion `Num < NumOperands && "Invalid child # of SDNode!"' failed.

It is because for certain cases foldBinOpIntoSelectIfProfitable may return a constant node when trueVal and falseVal of the select inst have the same value, at this time in following lowerSELECT it reports error that operands cannot be get from a constant node.

[llvmbot]

@llvm/issue-subscribers-backend-risc-v

Author: None (Yunzezhu94)

Here is a simple reduced case: `int a = (a ? 4 : 8) / (8 ? -5141143369814759789L : 0);` When compiling this case with order `clang++ -std=c++11 -march=rv64imafdc -mabi=lp64d -w -O0 -o a.o -c a.cpp` It reports error: llvm-project/llvm/include/llvm/CodeGen/SelectionDAGNodes.h:960: const llvm::SDValue& llvm::SDNode::getOperand(unsigned int) const: Assertion `Num < NumOperands && "Invalid child # of SDNode!"' failed.

It is because for certain cases foldBinOpIntoSelectIfProfitable may return a constant node when trueVal and falseVal of the select inst have the same value, at this time in following lowerSELECT it reports error that operands cannot be get from a constant node.