[AMDGPU] Only reinitialize disassembler Bytes array when needed. NFC.

[jayfoad]

No description provided.

[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Jay Foad (jayfoad)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/96666.diff

1 Files Affected:

• (modified) llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp (+6-6)

diff --git a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
index 76a559c9443bd..0c0e9163fc6ef 100644
--- a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
+++ b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
@@ -494,10 +494,10 @@ DecodeStatus AMDGPUDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
       if (isGFX12() &&
           tryDecodeInst(DecoderTableGFX12W6496, MI, DecW, Address, CS))
         break;
-    }
 
-    // Reinitialize Bytes
-    Bytes = Bytes_.slice(0, MaxInstBytesNum);
+      // Reinitialize Bytes
+      Bytes = Bytes_.slice(0, MaxInstBytesNum);
+    }
 
     if (Bytes.size() >= 8) {
       const uint64_t QW = eatBytes<uint64_t>(Bytes);
@@ -552,10 +552,10 @@ DecodeStatus AMDGPUDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
       if (isGFX12() &&
           tryDecodeInst(DecoderTableGFX12W6464, MI, QW, Address, CS))
         break;
-    }
 
-    // Reinitialize Bytes
-    Bytes = Bytes_.slice(0, MaxInstBytesNum);
+      // Reinitialize Bytes
+      Bytes = Bytes_.slice(0, MaxInstBytesNum);
+    }
 
     // Try decode 32-bit instruction
     if (Bytes.size() >= 4) {

[jayfoad]

Each "reinitialize" is now paired with the earlier "eatSomething(Bytes)" which mutated it.