[PATCH] D80637: [AMDGPU][MC][DISASSEMBLER] Corrected decoder to consume each code fragment once

[Dmitry Preobrazhensky via Phabricator via llvm-commits]

dp created this revision.
dp added reviewers: arsenm, rampitec.
Herald added subscribers: llvm-commits, kerbowa, hiraditya, t-tye, tpr, dstuttard, yaxunl, nhaehnle, wdng, jvesely, kzhuravl.
Herald added a project: LLVM.
dp added a child revision: D80636: [AMDGPU][MC] Corrected v_writelane_b32 to fix a decoding bug.

Current implementation may decode some fragments of code twice. This result in other bugs being hidden.

See detailed bug description <https://bugs.llvm.org/show_bug.cgi?id=46101>.

Decoding of v_writelane_b32 will be corrected by a separate change <https://reviews.llvm.org/D80636>.


https://reviews.llvm.org/D80637

Files:
  llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
  llvm/test/MC/Disassembler/AMDGPU/gfx10_dasm_all.txt


Index: llvm/test/MC/Disassembler/AMDGPU/gfx10_dasm_all.txt
===================================================================
--- llvm/test/MC/Disassembler/AMDGPU/gfx10_dasm_all.txt
+++ llvm/test/MC/Disassembler/AMDGPU/gfx10_dasm_all.txt
@@ -98025,7 +98025,7 @@
 # GFX10: v_trunc_f64_e64 v[5:6], |v[1:2]| ; encoding: [0x05,0x01,0x97,0xd5,0x01,0x01,0x00,0x00]
 0x05,0x01,0x97,0xd5,0x01,0x01,0x00,0x00
 
-# GFX10: v_writelane_b32 v255, 0, s2     ; encoding: [0xff,0x00,0x61,0xd7,0x80,0x04,0x00,0x00]
+# GFX10-FIXME: v_writelane_b32 v255, 0, s2     ; encoding: [0xff,0x00,0x61,0xd7,0x80,0x04,0x00,0x00]
 0xff,0x00,0x61,0xd7,0x80,0x04,0x00,0x00
 
 # GFX10: v_writelane_b32 v5, -1, s2      ; encoding: [0x05,0x00,0x61,0xd7,0xc1,0x04,0x00,0x00]
Index: llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
+++ llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
@@ -362,13 +362,6 @@
     Res = tryDecodeInst(DecoderTableGFX1064, MI, QW, Address);
   } while (false);
 
-  if (Res && (MaxInstBytesNum - Bytes.size()) == 12 && (!HasLiteral ||
-        !(MCII->get(MI.getOpcode()).TSFlags & SIInstrFlags::VOP3))) {
-    MaxInstBytesNum = 8;
-    Bytes = Bytes_.slice(0, MaxInstBytesNum);
-    eatBytes<uint64_t>(Bytes);
-  }
-
   if (Res && (MI.getOpcode() == AMDGPU::V_MAC_F32_e64_vi ||
               MI.getOpcode() == AMDGPU::V_MAC_F32_e64_gfx6_gfx7 ||
               MI.getOpcode() == AMDGPU::V_MAC_F32_e64_gfx10 ||


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