[AMDGPU] Ensure positive InstOffset for buffer operations #145504

aleksandar-amd · 2025-06-24T12:07:23Z

GFX12+ buffer ops require positive InstOffset per AMD hardware spec. Modified assembler/disassembler to reject negative buffer offsets.

github-actions · 2025-06-24T12:07:43Z

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llvmbot · 2025-06-24T12:08:11Z

@llvm/pr-subscribers-mc

@llvm/pr-subscribers-backend-amdgpu

Author: Aleksandar Spasojevic (aleksandar-amd)

Changes

GFX12+ buffer ops require positive InstOffset per AMD hardware spec. Modified assembler/disassembler to reject negative buffer offsets.

Full diff: https://github.com/llvm/llvm-project/pull/145504.diff

4 Files Affected:

(modified) llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp (+13-2)
(modified) llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp (+15)
(modified) llvm/test/MC/AMDGPU/gfx12_err.s (+258)
(added) llvm/test/MC/Disassembler/AMDGPU/gfx12_dasm_buffer_err.txt (+25)

diff --git a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
index 30dcd6d81f16d..2f759eb2609f1 100644
--- a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -4464,12 +4464,13 @@ bool AMDGPUAsmParser::validateOffset(const MCInst &Inst,
     return validateSMEMOffset(Inst, Operands);
 
   const auto &Op = Inst.getOperand(OpNum);
+  // GFX12+ buffer ops: InstOffset is signed 24, but must be positive
   if (isGFX12Plus() &&
       (TSFlags & (SIInstrFlags::MUBUF | SIInstrFlags::MTBUF))) {
     const unsigned OffsetSize = 24;
-    if (!isIntN(OffsetSize, Op.getImm())) {
+    if (!isUIntN(OffsetSize - 1, Op.getImm())) {
       Error(getFlatOffsetLoc(Operands),
-            Twine("expected a ") + Twine(OffsetSize) + "-bit signed offset");
+            Twine("expected a ") + Twine(OffsetSize - 1) + "-bit positive offset for buffer ops");
       return false;
     }
   } else {
@@ -4547,6 +4548,16 @@ bool AMDGPUAsmParser::validateSMEMOffset(const MCInst &Inst,
 
   uint64_t Offset = Op.getImm();
   bool IsBuffer = AMDGPU::getSMEMIsBuffer(Opcode);
+  // GFX12+ S_BUFFER_*: InstOffset is signed 24, but must be positive
+  if (isGFX12Plus() && IsBuffer) {
+    const unsigned OffsetSize = 24;
+    if (!isUIntN(OffsetSize, Offset)) {
+      Error(getSMEMOffsetLoc(Operands),
+            Twine("expected a ") + Twine(OffsetSize - 1) + "-bit positive offset for S_BUFFER ops");
+      return false;
+    }
+    return true;
+  }
   if (AMDGPU::isLegalSMRDEncodedUnsignedOffset(getSTI(), Offset) ||
       AMDGPU::isLegalSMRDEncodedSignedOffset(getSTI(), Offset, IsBuffer))
     return true;
diff --git a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
index 07a4292ef28bc..567d3e4ab6203 100644
--- a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
+++ b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
@@ -803,6 +803,21 @@ DecodeStatus AMDGPUDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
     }
   }
 
+  // Validate buffer offset for GFX12+ - must be positive
+  if ((MCII->get(MI.getOpcode()).TSFlags &
+       (SIInstrFlags::MTBUF | SIInstrFlags::MUBUF)) &&
+      AMDGPU::isGFX12Plus(STI)) {
+    int OffsetIdx =
+        AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::offset);
+    if (OffsetIdx != -1) {
+      uint32_t Imm = MI.getOperand(OffsetIdx).getImm();
+      int64_t SignedOffset = SignExtend64<24>(Imm);
+      if (SignedOffset < 0) {
+        return MCDisassembler::Fail;
+      }
+    }
+  }
+
   if (MCII->get(MI.getOpcode()).TSFlags &
       (SIInstrFlags::MTBUF | SIInstrFlags::MUBUF)) {
     int SWZOpIdx =
diff --git a/llvm/test/MC/AMDGPU/gfx12_err.s b/llvm/test/MC/AMDGPU/gfx12_err.s
index 9ddb91e25afe6..89278feb43ac3 100644
--- a/llvm/test/MC/AMDGPU/gfx12_err.s
+++ b/llvm/test/MC/AMDGPU/gfx12_err.s
@@ -125,3 +125,261 @@ s_alloc_vgpr exec
 
 s_alloc_vgpr vcc
 // GFX12-ERR: :[[@LINE-1]]:{{[0-9]+}}: error: invalid operand for instruction
+
+buffer_load_dword v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_dword v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_dwordx2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_dwordx3 v[0:2], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_dwordx4 v[0:3], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_short_d16 v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_format_d16_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_format_d16_xy v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_format_d16_xyz v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_format_d16_xyzw v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_short_d16_hi v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_format_d16_hi_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_sbyte_d16_hi v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_ubyte_d16_hi v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_sbyte_d16 v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_ubyte_d16 v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_sbyte v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_sshort v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_ubyte v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_load_ushort v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_byte v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_short v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_dword v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_dwordx2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_dwordx3 v[0:2], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_dwordx4 v[0:3], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_format_d16_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_format_d16_xy v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_format_d16_xyz v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_format_d16_xyzw v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_byte_d16_hi v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_short_d16_hi v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_store_format_d16_hi_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_add v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_add_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_and v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_and_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_cmpswap v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_cmpswap_x2 v[0:3], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_csub v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_dec v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_dec_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_inc v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_inc_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_fmax v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_smax v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_smax_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_umax v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_umax_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_fmin v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_smin v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_smin_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_umin v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_umin_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_or v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_or_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_sub v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_sub_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_swap v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_swap_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_xor v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+buffer_atomic_xor_x2 v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_d16_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_d16_xy v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_d16_xyz v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_d16_xyzw v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_xy v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_xyz v[0:2], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_load_format_xyzw v[0:3], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_d16_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_d16_xy v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_d16_xyz v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_d16_xyzw v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_x v0, off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_xy v[0:1], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_xyz v[0:2], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+tbuffer_store_format_xyzw v[0:3], off, s[4:7], s8 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for buffer ops
+
+s_buffer_load_b32 s5, s[4:7], s0 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_load_b64 s[10:11], s[4:7], s0 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_load_b96 s[20:22], s[4:7], s0 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_load_i8 s5, s[4:7], s0 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_load_u8 s5, s[4:7], s0 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_load_i16 s5, s[4:7], s0 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_load_u16 s5, s[4:7], s0 offset:-1
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_prefetch_data s[20:23], -1, s10, 7
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
\ No newline at end of file
diff --git a/llvm/test/MC/Disassembler/AMDGPU/gfx12_dasm_buffer_err.txt b/llvm/test/MC/Disassembler/AMDGPU/gfx12_dasm_buffer_err.txt
new file mode 100644
index 0000000000000..d58a7e9b6116a
--- /dev/null
+++ b/llvm/test/MC/Disassembler/AMDGPU/gfx12_dasm_buffer_err.txt
@@ -0,0 +1,25 @@
+# RUN: not llvm-mc -disassemble -triple=amdgcn -mcpu=gfx1200 -show-encoding %s 2>&1 | FileCheck --implicit-check-not=warning: --check-prefix=GFX12 %s
+
+# buffer_load_b32 v1, off, s[0:3], s4 offset:-1
+# GFX12: warning: invalid instruction encoding
+[0x04,0x00,0x05,0xc4,0x01,0x00,0x80,0x00,0xff,0xff,0xff,0xff]
+
+# buffer_load_b32 v0, off, s[4:7], s8 offset:-1
+# GFX12: warning: invalid instruction encoding
+[0x08,0x00,0x05,0xc4,0x00,0x08,0x80,0x00,0xff,0xff,0xff,0xff]
+
+# buffer_load_b64 v[0:1], off, s[4:7], s8 offset:-1
+# GFX12: warning: invalid instruction encoding
+[0x08,0x40,0x05,0xc4,0x00,0x08,0x80,0x00,0xff,0xff,0xff,0xff]
+
+# buffer_store_b32 v0, off, s[4:7], s8 offset:-1
+# GFX12: warning: invalid instruction encoding
+[0x08,0x80,0x06,0xc4,0x00,0x08,0x80,0x00,0xff,0xff,0xff,0xff]
+
+# buffer_atomic_add v0, off, s[4:7], s8 offset:-1
+# GFX12: warning: invalid instruction encoding
+[0x08,0x40,0x0d,0xc4,0x00,0x08,0x80,0x00,0xff,0xff,0xff,0xff]
+
+# tbuffer_load_format_x v0, off, s[4:7], s8 format:0 offset:-1
+# GFX12: warning: invalid instruction encoding
+[0x08,0x00,0x20,0xc4,0x00,0x08,0x00,0x00,0xff,0xff,0xff,0xff]
\ No newline at end of file

arsenm · 2025-06-24T12:15:12Z

llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp

+  // Validate buffer offset for GFX12+ - must be positive
+  if ((MCII->get(MI.getOpcode()).TSFlags &
+       (SIInstrFlags::MTBUF | SIInstrFlags::MUBUF)) &&
+      AMDGPU::isGFX12Plus(STI)) {


Avoid generation checks

But this check is only required for GFX12+ as the task specifies

The property is not gfx12+, the property is this specific opcode supports the offset or not.

jayfoad · 2025-06-24T13:35:27Z

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

@@ -4547,6 +4548,16 @@ bool AMDGPUAsmParser::validateSMEMOffset(const MCInst &Inst,

  uint64_t Offset = Op.getImm();
  bool IsBuffer = AMDGPU::getSMEMIsBuffer(Opcode);
+  // GFX12+ S_BUFFER_*: InstOffset is signed 24, but must be positive
+  if (isGFX12Plus() && IsBuffer) {


Would it be neater to put this logic inside isLegalSMRDEncodedSignedOffset?

shiltian · 2025-06-24T13:37:34Z

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

@@ -4547,6 +4548,16 @@ bool AMDGPUAsmParser::validateSMEMOffset(const MCInst &Inst,

  uint64_t Offset = Op.getImm();
  bool IsBuffer = AMDGPU::getSMEMIsBuffer(Opcode);
+  // GFX12+ S_BUFFER_*: InstOffset is signed 24, but must be positive
+  if (isGFX12Plus() && IsBuffer) {
+    const unsigned OffsetSize = 24;


nit:

Suggested change

const unsigned OffsetSize = 24;

constexpr const unsigned OffsetSize = 24;

shiltian · 2025-06-24T13:38:08Z

llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp

+      if (SignedOffset < 0) {
+        return MCDisassembler::Fail;
+      }


Suggested change

if (SignedOffset < 0) {

return MCDisassembler::Fail;

}

if (SignedOffset < 0)

return MCDisassembler::Fail;

shiltian · 2025-06-24T13:39:03Z

llvm/test/MC/AMDGPU/gfx12_err.s

+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops
+
+s_buffer_prefetch_data s[20:23], -1, s10, 7
+// GFX12-ERR: [[@LINE-1]]:{{[0-9]+}}: error: expected a 23-bit positive offset for S_BUFFER ops


missing the empty line at EOF

GFX12+ buffer ops require positive InstOffset per AMD hardware spec. Modified assembler/disassembler to reject negative buffer offsets.

Resolving comments from review.

jayfoad · 2025-06-25T08:59:59Z

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

      Error(getFlatOffsetLoc(Operands),
-            Twine("expected a ") + Twine(OffsetSize) + "-bit signed offset");
+            Twine("expected a ") + Twine(OffsetSize - 1) + "-bit positive offset for buffer ops");


"non-negative" is more correct than "positive", since 0 is OK. Same in the rest of the patch.

jayfoad · 2025-06-25T09:00:27Z

llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp

+  // Generate appropriate error message based on generation and buffer type
+  if (isGFX12Plus() && IsBuffer)
+    Error(getSMEMOffsetLoc(Operands),
+          "expected a 23-bit positive offset for S_BUFFER ops");
+  else
+    Error(getSMEMOffsetLoc(Operands),
+          isGFX12Plus()          ? "expected a 24-bit signed offset"
+          : (isVI() || IsBuffer) ? "expected a 20-bit unsigned offset"
+                                 : "expected a 21-bit signed offset");


Please refactor to choose the correct error string first, and then have a single call to Error.

jayfoad · 2025-06-25T09:04:05Z

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

+      if (IsBuffer) {
+        constexpr const unsigned OffsetSize = 23;
+        return isUIntN(OffsetSize, EncodedOffset);
+      }


Indentation looks wrong here. Also this is simpler:

Suggested change

if (IsBuffer) {

constexpr const unsigned OffsetSize = 23;

return isUIntN(OffsetSize, EncodedOffset);

}

if (IsBuffer && EncodedOffset < 0)

return false;

llvmbot added backend:AMDGPU mc Machine (object) code labels Jun 24, 2025

arsenm reviewed Jun 24, 2025

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mbrkusanin requested review from jayfoad and dstutt June 24, 2025 13:29

jayfoad reviewed Jun 24, 2025

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shiltian reviewed Jun 24, 2025

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aleksandar-amd added 2 commits June 24, 2025 16:52

[AMDGPU] Ensure positive InstOffset for buffer operations

81fc7eb

GFX12+ buffer ops require positive InstOffset per AMD hardware spec. Modified assembler/disassembler to reject negative buffer offsets.

[AMDGPU] Fix buffer offset validation per PR feedback

3470988

Resolving comments from review.

aleksandar-amd force-pushed the amdgpu-gfx12-buffer-instoffset-positive branch from 8cb7b4f to 3470988 Compare June 24, 2025 14:58

jayfoad reviewed Jun 25, 2025

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[AMDGPU] Ensure positive InstOffset for buffer operations #145504

[AMDGPU] Ensure positive InstOffset for buffer operations #145504

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	const unsigned OffsetSize = 24;
	constexpr const unsigned OffsetSize = 24;

[AMDGPU] Ensure positive InstOffset for buffer operations #145504

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[AMDGPU] Ensure positive InstOffset for buffer operations #145504

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