[llvm] [AMDGPU] Support merging 16-bit and 8-bit TBUFFER load/store instruction (PR #145078)

[Jay Foad via llvm-commits]

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@@ -839,8 +839,16 @@ void SILoadStoreOptimizer::CombineInfo::setMI(MachineBasicBlock::iterator MI,
     Offset = I->getOperand(OffsetIdx).getImm();
   }
 
-  if (InstClass == TBUFFER_LOAD || InstClass == TBUFFER_STORE)
+  if (InstClass == TBUFFER_LOAD || InstClass == TBUFFER_STORE) {
     Format = LSO.TII->getNamedOperand(*I, AMDGPU::OpName::format)->getImm();
+    const AMDGPU::GcnBufferFormatInfo *Info =
+        AMDGPU::getGcnBufferFormatInfo(Format, *LSO.STM);
+
+    // Use 2-byte element size if the tbuffer format is 16-bit.
+    // Use 1-byte element size if the tbuffer format is 8-bit.
+    if (Info)
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jayfoad wrote:

I think it would be better to change this pass so that if `!Info` then the instruction is not added to the list of mergeable instructions. I.e. either change `setMI` so that it can return failure, or check that `getGcnBufferFormatInfo` succeeds before calling `setMI`. I think this is safer than treating unknown formats as if they are 32-bit.

https://github.com/llvm/llvm-project/pull/145078