[PATCH] D155587: [AMDGPU][RFC] Update isLegalAddressingMode for GFX9 SMEM signed offsets

[Jay Foad via Phabricator via llvm-commits]

foad updated this revision to Diff 541479.
foad added a comment.

Fix comment


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D155587/new/

https://reviews.llvm.org/D155587

Files:
  llvm/lib/Target/AMDGPU/SIISelLowering.cpp


Index: llvm/lib/Target/AMDGPU/SIISelLowering.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -1388,12 +1388,16 @@
       // in 8-bits, it can use a smaller encoding.
       if (!isUInt<32>(AM.BaseOffs / 4))
         return false;
-    } else if (Subtarget->getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS) {
+    } else if (Subtarget->getGeneration() < AMDGPUSubtarget::GFX9) {
       // On VI, these use the SMEM format and the offset is 20-bit in bytes.
       if (!isUInt<20>(AM.BaseOffs))
         return false;
-    } else
-      llvm_unreachable("unhandled generation");
+    } else {
+      // On GFX9 the offset is signed 21-bit in bytes (but must not be negative
+      // for S_BUFFER_* instructions).
+      if (!isInt<21>(AM.BaseOffs))
+        return false;
+    }
 
     if (AM.Scale == 0) // r + i or just i, depending on HasBaseReg.
       return true;


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