[llvm] [AMDGPU] Handle MachineOperandType global address in SIFoldOperands. (PR #135424)

[Dhruva Chakrabarti via llvm-commits]

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@@ -1161,6 +1161,10 @@ void SIFoldOperandsImpl::foldOperand(
 
         if (OpToFold.isImm())
           UseMI->getOperand(1).ChangeToImmediate(OpToFold.getImm());
+        else if (OpToFold.isGlobal())
+          UseMI->getOperand(1).ChangeToGA(OpToFold.getGlobal(),
+                                          OpToFold.getOffset(),
+                                          OpToFold.getTargetFlags());
         else
           UseMI->getOperand(1).ChangeToFrameIndex(OpToFold.getIndex());
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dhruvachak wrote:

> I can modify the patch to the first approach you mention here. Since we enter this block only in case `FoldingImmLike` is true and this variable is a bool for either immediate, frame index or global values. The if-else if-else conditions focus on only these 3 operands so there won't be any edge case for the else condition as we enter the block when it is one of the 3 operands.
> 
> But I'm not clear on how/where should I move the setDesc() to, since it is almost at the top of the block and the if-else if-else is immediately after it.
> 
> The structure is ->
> 
> if(FoldingImmLike){ if(execMaybeModifiedBeforeUse) return; UseMI->setDesc() // at the top of the block, in case the exec flag immediately above is false if-else if-else block UseMI->removeOperand(2) return; }
> 
> Where should I place setDesc() to avoid a side effect?

I think setDesc() has to be sunk only if you bail out. How about the following?

if (isImm()) {}
else if (isFI()) {}
else {
  assert(isGlobal());
  ...
}
Then you don't need to move setDesc().

https://github.com/llvm/llvm-project/pull/135424