[llvm] [AMDGPU] Fix negative immediate offset for unbuffered smem loads (PR #79553)

[via llvm-commits]

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@@ -2096,21 +2099,53 @@ bool AMDGPUDAGToDAGISel::SelectSMRDBaseOffset(SDValue Addr, SDValue &SBase,
   }
   if (!N0 || !N1)
     return false;
+
+  bool Selected = false;
   if (SelectSMRDOffset(N1, SOffset, Offset, Imm32Only, IsBuffer)) {
     SBase = N0;
-    return true;
-  }
-  if (SelectSMRDOffset(N0, SOffset, Offset, Imm32Only, IsBuffer)) {
+    Selected = true;
+  } else if (SelectSMRDOffset(N0, SOffset, Offset, Imm32Only, IsBuffer)) {
     SBase = N1;
+    Selected = true;
+  }
+
+  if (Selected) {
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vangthao95 wrote:

I moved this code inside SelectSMRDOffset() where the offset is selected to make it clearer. Although for when sgpr[offset] (SOffset) is present, the offset is selected first before SOffset is selected so I had to adjust it after.

https://github.com/llvm/llvm-project/pull/79553