================
@@ -188,6 +190,37 @@ void
DivergenceLoweringHelper::constrainAsLaneMask(Incoming &In) {
In.Reg = Copy.getReg(0);
}
+void replaceUsesOfRegInInstWith(Register Reg, MachineInstr *Inst,
+ Register NewReg) {
+ for (MachineOperand &Op : Inst->operands()) {
+ if (Op.isReg() && Op.getReg() == Reg)
+ Op.setReg(NewReg);
+ }
+}
+
+bool DivergenceLoweringHelper::lowerTempDivergence() {
+ AMDGPU::IntrinsicLaneMaskAnalyzer ILMA(*MF);
+
+ for (auto [Inst, UseInst, _] : MUI->getUsesOutsideCycleWithDivergentExit()) {
+ Register Reg = Inst->getOperand(0).getReg();
+ if (MRI->getType(Reg) == LLT::scalar(1) || MUI->isDivergent(Reg) ||
+ ILMA.isS32S64LaneMask(Reg))
+ continue;
+
+ MachineInstr *MI = const_cast<MachineInstr *>(Inst);
----------------
nhaehnle wrote:
These come out of the analysis. The analysis itself uses const
pointers/references in its implementation, which I believe is a good idea for
const correctness. I wouldn't change that.
So a `const_cast` is needed at some point. The only question is where.
I think here is as good a place as any, though perhaps grouping them together
with a small explanation is in order. Something like:
```c++
// As an analysis, UniformityAnalysis treats instructions as const. We have
the parent function
// as non-const, so casting const away here is inelegant but justified.
MachineInstr *MI = const_cast<MachineInstr *>(Inst);
MachineInstr *UseMI = const_cast<MachineInstr *>(UseInst);
```
https://github.com/llvm/llvm-project/pull/124298
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