[AMDGPU][MC] Disassembler warning for v_cmpx instructions #127925

jwanggit86 · 2025-02-20T00:33:42Z

For GFX10+ the destnation reg of v_cmpx instructions is implicitly EXEC, which is encoded as 0x7E. However, the disassembler does not check this field, thus allowing any value. With this patch, if the field is not 0x7E a warning is issued.

llvmbot · 2025-02-20T00:34:03Z

@llvm/pr-subscribers-backend-amdgpu

@llvm/pr-subscribers-mc

Author: Jun Wang (jwanggit86)

Changes

For GFX10+ the destnation reg of v_cmpx instructions is implicitly EXEC, which is encoded as 0x7E. However, the disassembler does not check this field, thus allowing any value. With this patch, if the field is not 0x7E a warning is issued.

Patch is 22.34 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/127925.diff

2 Files Affected:

(modified) llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp (+11-1)
(added) llvm/test/MC/Disassembler/AMDGPU/gfx10_vop3cx_warn.txt (+407)

diff --git a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
index 308ab8e3b82c4..cd74ff5a34c42 100644
--- a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
+++ b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
@@ -663,6 +663,8 @@ DecodeStatus AMDGPUDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
     return MCDisassembler::Fail;
   } while (false);
 
+  DecodeStatus Status = MCDisassembler::Success;
+
   if (MCII->get(MI.getOpcode()).TSFlags & SIInstrFlags::DPP) {
     if (isMacDPP(MI))
       convertMacDPPInst(MI);
@@ -801,8 +803,16 @@ DecodeStatus AMDGPUDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
   if (ImmLitIdx != -1 && !IsSOPK)
     convertFMAanyK(MI, ImmLitIdx);
 
+  if (isGFX10Plus() &&
+      (MCII->get(MI.getOpcode()).TSFlags & SIInstrFlags::VOP3) &&
+      MCII->get(MI.getOpcode()).hasImplicitDefOfPhysReg(AMDGPU::EXEC)) {
+    auto ExecEncoding = MRI.getEncodingValue(AMDGPU::EXEC_LO);
+    if (Bytes_[0] != ExecEncoding)
+      Status = MCDisassembler::SoftFail;
+  }
+
   Size = MaxInstBytesNum - Bytes.size();
-  return MCDisassembler::Success;
+  return Status;
 }
 
 void AMDGPUDisassembler::convertEXPInst(MCInst &MI) const {
diff --git a/llvm/test/MC/Disassembler/AMDGPU/gfx10_vop3cx_warn.txt b/llvm/test/MC/Disassembler/AMDGPU/gfx10_vop3cx_warn.txt
new file mode 100644
index 0000000000000..b8bf696cf9fd3
--- /dev/null
+++ b/llvm/test/MC/Disassembler/AMDGPU/gfx10_vop3cx_warn.txt
@@ -0,0 +1,407 @@
+# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1010 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefixes=GFX10 %s
+
+### class
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_class_f16_e64 v1, v2             ; encoding: [0x7e,0x00,0x9f,0xd4,0x01,0x05,0x02,0x00]
+0x00,0x00,0x9f,0xd4,0x01,0x05,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_class_f32_e64 v1, v2             ; encoding: [0x7e,0x00,0x98,0xd4,0x01,0x05,0x02,0x00]
+0x01,0x00,0x98,0xd4,0x01,0x05,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_class_f64_e64 s[4:5], v2         ; encoding: [0x7e,0x00,0xb8,0xd4,0x04,0x04,0x02,0x00]
+0x02,0x00,0xb8,0xd4,0x04,0x04,0x02,0x00
+
+### eq
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_f16_e64 0.5, v2               ; encoding: [0x7e,0x00,0xda,0xd4,0xf0,0x04,0x02,0x00]
+0x03,0x00,0xda,0xd4,0xf0,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_f32_e64 -4.0, v2              ; encoding: [0x7e,0x00,0x12,0xd4,0xf7,0x04,0x02,0x00]
+0x04,0x00,0x12,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_f64_e64 v[1:2], -4.0          ; encoding: [0x7e,0x00,0x32,0xd4,0x01,0xef,0x01,0x00]
+0x05,0x00,0x32,0xd4,0x01,0xef,0x01,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_i16_e64 -1, v2                ; encoding: [0x7e,0x00,0x9a,0xd4,0xc1,0x04,0x02,0x00]
+0x06,0x00,0x9a,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_i32_e64 -1, v2                ; encoding: [0x7e,0x00,0x92,0xd4,0xc1,0x04,0x02,0x00]
+0x07,0x00,0x92,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_i64_e64 -1, v[2:3]            ; encoding: [0x7e,0x00,0xb2,0xd4,0xc1,0x04,0x02,0x00]
+0x08,0x00,0xb2,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_u16_e64 s1, v2                ; encoding: [0x7e,0x00,0xba,0xd4,0x01,0x04,0x02,0x00]
+0x09,0x00,0xba,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_u32_e64 s1, v2                ; encoding: [0x7e,0x00,0xd2,0xd4,0x01,0x04,0x02,0x00]
+0x0a,0x00,0xd2,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_eq_u64_e64 s[2:3], v[2:3]        ; encoding: [0x7e,0x00,0xf2,0xd4,0x02,0x04,0x02,0x00]
+0x0b,0x00,0xf2,0xd4,0x02,0x04,0x02,0x00
+
+### f_f
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_f_f16_e64 -4.0, v2               ; encoding: [0x7e,0x00,0xd8,0xd4,0xf7,0x04,0x02,0x00]
+0x0c,0x00,0xd8,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_f_f32_e64 -4.0, v2               ; encoding: [0x7e,0x00,0x10,0xd4,0xf7,0x04,0x02,0x00]
+0x0d,0x00,0x10,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_f_f64_e64 -4.0, v[2:3]           ; encoding: [0x7e,0x00,0x30,0xd4,0xf7,0x04,0x02,0x00]
+0x0e,0x00,0x30,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_f_i32_e64 -1, v2                 ; encoding: [0x7e,0x00,0x90,0xd4,0xc1,0x04,0x02,0x00]
+0x0f,0x00,0x90,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_f_i64_e64 -1, v[2:3]             ; encoding: [0x7e,0x00,0xb0,0xd4,0xc1,0x04,0x02,0x00]
+0x10,0x00,0xb0,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_f_u32_e64 s1, v2                 ; encoding: [0x7e,0x00,0xd0,0xd4,0x01,0x04,0x02,0x00]
+0x11,0x00,0xd0,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_f_u64_e64 s[2:3], v[2:3]         ; encoding: [0x7e,0x00,0xf0,0xd4,0x02,0x04,0x02,0x00]
+0x12,0x00,0xf0,0xd4,0x02,0x04,0x02,0x00
+
+### ge
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_f16_e64 -4.0, v2              ; encoding: [0x7e,0x00,0xde,0xd4,0xf7,0x04,0x02,0x00]
+0x13,0x00,0xde,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_f32_e64 -4.0, v2              ; encoding: [0x7e,0x00,0x16,0xd4,0xf7,0x04,0x02,0x00]
+0x14,0x00,0x16,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_f64_e64 -4.0, v[2:3]          ; encoding: [0x7e,0x00,0x36,0xd4,0xf7,0x04,0x02,0x00]
+0x15,0x00,0x36,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_i16_e64 -1, v2                ; encoding: [0x7e,0x00,0x9e,0xd4,0xc1,0x04,0x02,0x00]
+0x16,0x00,0x9e,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_i32_e64 -1, v2                ; encoding: [0x7e,0x00,0x96,0xd4,0xc1,0x04,0x02,0x00]
+0x17,0x00,0x96,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_i64_e64 -1, v[2:3]            ; encoding: [0x7e,0x00,0xb6,0xd4,0xc1,0x04,0x02,0x00]
+0x18,0x00,0xb6,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_u16_e64 -1, v2                ; encoding: [0x7e,0x00,0xbe,0xd4,0xc1,0x04,0x02,0x00]
+0x19,0x00,0xbe,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_u16_e64 v1, m0                ; encoding: [0x7e,0x00,0xbe,0xd4,0x01,0xf9,0x00,0x00]
+0x1a,0x00,0xbe,0xd4,0x01,0xf9,0x00,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_u32_e64 v1, m0                ; encoding: [0x7e,0x00,0xd6,0xd4,0x01,0xf9,0x00,0x00]
+0x1b,0x00,0xd6,0xd4,0x01,0xf9,0x00,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ge_u64_e64 exec, v[2:3]          ; encoding: [0x7e,0x00,0xf6,0xd4,0x7e,0x04,0x02,0x00]
+0x1c,0x00,0xf6,0xd4,0x7e,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_f16_e64 -4.0, v2              ; encoding: [0x7e,0x00,0xdc,0xd4,0xf7,0x04,0x02,0x00]
+0x1d,0x00,0xdc,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_f32_e64 -4.0, v2              ; encoding: [0x7e,0x00,0x14,0xd4,0xf7,0x04,0x02,0x00]
+0x1e,0x00,0x14,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_f64_e64 -4.0, v[2:3]          ; encoding: [0x7e,0x00,0x34,0xd4,0xf7,0x04,0x02,0x00]
+0x1f,0x00,0x34,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_i16_e64 -1, v2                ; encoding: [0x7e,0x00,0x9c,0xd4,0xc1,0x04,0x02,0x00]
+0x20,0x00,0x9c,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_i32_e64 -1, v2                ; encoding: [0x7e,0x00,0x94,0xd4,0xc1,0x04,0x02,0x00]
+0x21,0x00,0x94,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_i64_e64 -1, v[2:3]            ; encoding: [0x7e,0x00,0xb4,0xd4,0xc1,0x04,0x02,0x00]
+0x22,0x00,0xb4,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_u16_e64 s1, v2                ; encoding: [0x7e,0x00,0xbc,0xd4,0x01,0x04,0x02,0x00]
+0x23,0x00,0xbc,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_u32_e64 s1, v2                ; encoding: [0x7e,0x00,0xd4,0xd4,0x01,0x04,0x02,0x00]
+0x24,0x00,0xd4,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_gt_u64_e64 s[2:3], v[2:3]        ; encoding: [0x7e,0x00,0xf4,0xd4,0x02,0x04,0x02,0x00]
+0x25,0x00,0xf4,0xd4,0x02,0x04,0x02,0x00
+
+### le
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_f16_e64 -4.0, v2              ; encoding: [0x7e,0x00,0xdb,0xd4,0xf7,0x04,0x02,0x00]
+0x26,0x00,0xdb,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_f32_e64 -4.0, v2              ; encoding: [0x7e,0x00,0x13,0xd4,0xf7,0x04,0x02,0x00]
+0x27,0x00,0x13,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_f64_e64 -4.0, v[2:3]          ; encoding: [0x7e,0x00,0x33,0xd4,0xf7,0x04,0x02,0x00]
+0x28,0x00,0x33,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_i16_e64 -1, v2                ; encoding: [0x7e,0x00,0x9b,0xd4,0xc1,0x04,0x02,0x00]
+0x29,0x00,0x9b,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_i32_e64 -1, v2                ; encoding: [0x7e,0x00,0x93,0xd4,0xc1,0x04,0x02,0x00]
+0x2a,0x00,0x93,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_i64_e64 -1, v[2:3]            ; encoding: [0x7e,0x00,0xb3,0xd4,0xc1,0x04,0x02,0x00]
+0x2b,0x00,0xb3,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_u16_e64 s1, v2                ; encoding: [0x7e,0x00,0xbb,0xd4,0x01,0x04,0x02,0x00]
+0x2e,0x00,0xbb,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_u32_e64 s1, v2                ; encoding: [0x7e,0x00,0xd3,0xd4,0x01,0x04,0x02,0x00]
+0x2f,0x00,0xd3,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_le_u64_e64 s[2:3], v[2:3]        ; encoding: [0x7e,0x00,0xf3,0xd4,0x02,0x04,0x02,0x00]
+0x30,0x00,0xf3,0xd4,0x02,0x04,0x02,0x00
+
+### lg
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lg_f16_e64 -4.0, v2              ; encoding: [0x7e,0x00,0xdd,0xd4,0xf7,0x04,0x02,0x00]
+0x31,0x00,0xdd,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lg_f32_e64 -4.0, v2              ; encoding: [0x7e,0x00,0x15,0xd4,0xf7,0x04,0x02,0x00]
+0x32,0x00,0x15,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lg_f64_e64 -4.0, v[2:3]          ; encoding: [0x7e,0x00,0x35,0xd4,0xf7,0x04,0x02,0x00]
+0x33,0x00,0x35,0xd4,0xf7,0x04,0x02,0x00
+
+### lt
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_f16_e64 -4.0, v2              ; encoding: [0x7e,0x00,0xd9,0xd4,0xf7,0x04,0x02,0x00]
+0x34,0x00,0xd9,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_f32_e64 -4.0, v2              ; encoding: [0x7e,0x00,0x11,0xd4,0xf7,0x04,0x02,0x00]
+0x35,0x00,0x11,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_f64_e64 -4.0, v[2:3]          ; encoding: [0x7e,0x00,0x31,0xd4,0xf7,0x04,0x02,0x00]
+0x36,0x00,0x31,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_i16_e64 -1, v2                ; encoding: [0x7e,0x00,0x99,0xd4,0xc1,0x04,0x02,0x00]
+0x37,0x00,0x99,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_i32_e64 -1, v2                ; encoding: [0x7e,0x00,0x91,0xd4,0xc1,0x04,0x02,0x00]
+0x38,0x00,0x91,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_i64_e64 -1, v[2:3]            ; encoding: [0x7e,0x00,0xb1,0xd4,0xc1,0x04,0x02,0x00]
+0x39,0x00,0xb1,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_u16_e64 s1, v2                ; encoding: [0x7e,0x00,0xb9,0xd4,0x01,0x04,0x02,0x00]
+0x3a,0x00,0xb9,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_u32_e64 s1, v2                ; encoding: [0x7e,0x00,0xd1,0xd4,0x01,0x04,0x02,0x00]
+0x3b,0x00,0xd1,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_lt_u64_e64 s[2:3], v[2:3]        ; encoding: [0x7e,0x00,0xf1,0xd4,0x02,0x04,0x02,0x00]
+0x3c,0x00,0xf1,0xd4,0x02,0x04,0x02,0x00
+
+### ne
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ne_i16_e64 -1, v2                ; encoding: [0x7e,0x00,0x9d,0xd4,0xc1,0x04,0x02,0x00]
+0x3d,0x00,0x9d,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ne_i32_e64 -1, v2                ; encoding: [0x7e,0x00,0x95,0xd4,0xc1,0x04,0x02,0x00]
+0x3e,0x00,0x95,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ne_i64_e64 -1, v[2:3]            ; encoding: [0x7e,0x00,0xb5,0xd4,0xc1,0x04,0x02,0x00]
+0x3f,0x00,0xb5,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ne_u16_e64 s1, v2                ; encoding: [0x7e,0x00,0xbd,0xd4,0x01,0x04,0x02,0x00]
+0x40,0x00,0xbd,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ne_u32_e64 s1, v2                ; encoding: [0x7e,0x00,0xd5,0xd4,0x01,0x04,0x02,0x00]
+0x41,0x00,0xd5,0xd4,0x01,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ne_u64_e64 s[2:3], v[2:3]        ; encoding: [0x7e,0x00,0xf5,0xd4,0x02,0x04,0x02,0x00]
+0x42,0x00,0xf5,0xd4,0x02,0x04,0x02,0x00
+
+### neq
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_neq_f16_e64 -4.0, v2             ; encoding: [0x7e,0x00,0xfd,0xd4,0xf7,0x04,0x02,0x00]
+0x43,0x00,0xfd,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_neq_f32_e64 -4.0, v2             ; encoding: [0x7e,0x00,0x1d,0xd4,0xf7,0x04,0x02,0x00]
+0x44,0x00,0x1d,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_neq_f64_e64 -4.0, v[2:3]         ; encoding: [0x7e,0x00,0x3d,0xd4,0xf7,0x04,0x02,0x00]
+0x45,0x00,0x3d,0xd4,0xf7,0x04,0x02,0x00
+
+### nge
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nge_f16_e64 -4.0, v2             ; encoding: [0x7e,0x00,0xf9,0xd4,0xf7,0x04,0x02,0x00]
+0x46,0x00,0xf9,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nge_f32_e64 -4.0, v2             ; encoding: [0x7e,0x00,0x19,0xd4,0xf7,0x04,0x02,0x00]
+0x47,0x00,0x19,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nge_f64_e64 -4.0, v[2:3]         ; encoding: [0x7e,0x00,0x39,0xd4,0xf7,0x04,0x02,0x00]
+0x48,0x00,0x39,0xd4,0xf7,0x04,0x02,0x00
+
+### ngt
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ngt_f16_e64 -4.0, v2             ; encoding: [0x7e,0x00,0xfb,0xd4,0xf7,0x04,0x02,0x00]
+0x49,0x00,0xfb,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ngt_f32_e64 -4.0, v2             ; encoding: [0x7e,0x00,0x1b,0xd4,0xf7,0x04,0x02,0x00]
+0x4a,0x00,0x1b,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_ngt_f64_e64 -4.0, v[2:3]         ; encoding: [0x7e,0x00,0x3b,0xd4,0xf7,0x04,0x02,0x00]
+0x4b,0x00,0x3b,0xd4,0xf7,0x04,0x02,0x00
+
+### nle
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nle_f16_e64 -1, v2               ; encoding: [0x7e,0x00,0xfc,0xd4,0xc1,0x04,0x02,0x00]
+0x4c,0x00,0xfc,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nle_f32_e64 -1, v2               ; encoding: [0x7e,0x00,0x1c,0xd4,0xc1,0x04,0x02,0x00]
+0x4d,0x00,0x1c,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nle_f64_e64 -1, v[2:3]           ; encoding: [0x7e,0x00,0x3c,0xd4,0xc1,0x04,0x02,0x00]
+0x4e,0x00,0x3c,0xd4,0xc1,0x04,0x02,0x00
+
+### nlg
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nlg_f16_e64 -1, v2               ; encoding: [0x7e,0x00,0xfa,0xd4,0xc1,0x04,0x02,0x00]
+0x4f,0x00,0xfa,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nlg_f32_e64 -1, v2               ; encoding: [0x7e,0x00,0x1a,0xd4,0xc1,0x04,0x02,0x00]
+0x50,0x00,0x1a,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nlg_f64_e64 -1, v[2:3]           ; encoding: [0x7e,0x00,0x3a,0xd4,0xc1,0x04,0x02,0x00]
+0x51,0x00,0x3a,0xd4,0xc1,0x04,0x02,0x00
+
+### nlt
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nlt_f16_e64 -1, v2               ; encoding: [0x7e,0x00,0xfe,0xd4,0xc1,0x04,0x02,0x00]
+0x52,0x00,0xfe,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nlt_f32_e64 -1, v2               ; encoding: [0x7e,0x00,0x1e,0xd4,0xc1,0x04,0x02,0x00]
+0x53,0x00,0x1e,0xd4,0xc1,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_nlt_f64_e64 -1, v[2:3]           ; encoding: [0x7e,0x00,0x3e,0xd4,0xc1,0x04,0x02,0x00]
+0x54,0x00,0x3e,0xd4,0xc1,0x04,0x02,0x00
+
+### o_f
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_o_f16_e64 -4.0, v2               ; encoding: [0x7e,0x00,0xdf,0xd4,0xf7,0x04,0x02,0x00]
+0x55,0x00,0xdf,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_o_f32_e64 -4.0, v2               ; encoding: [0x7e,0x00,0x17,0xd4,0xf7,0x04,0x02,0x00]
+0x56,0x00,0x17,0xd4,0xf7,0x04,0x02,0x00
+
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding
+# v_cmpx_o_f64_e64 -4.0, v[2:3]           ; encoding: [0x7e,0x00,0x37,0xd4,0xf7,0x04,0x02,0x00]
+0x57,0x00,0x37,0xd4,0xf7,0x04,0x02,0x00
+
+### t_i
+# GFX10: [...
[truncated]

arsenm · 2025-02-20T02:57:54Z

llvm/test/MC/Disassembler/AMDGPU/gfx10_vop3cx_warn.txt

+# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1010 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefixes=GFX10 %s
+
+### class
+# GFX10: [[@LINE+2]]:1: warning: potentially undefined instruction encoding


It would be nice if the instruction was more specific

See PR 128256.

arsenm · 2025-02-20T02:58:17Z

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

@@ -801,8 +803,16 @@ DecodeStatus AMDGPUDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
  if (ImmLitIdx != -1 && !IsSOPK)
    convertFMAanyK(MI, ImmLitIdx);

+  if (isGFX10Plus() &&


As always, I despise generation checks. Can you comment this, or put it in some kind of named predicate function

This particular generation check may not be necessary. It seems that pre-gfx10 the VOPC instructions in question are not encoded as VOP3.

This check is removed in the latest commit.

Sisyph

The approach seems good.

Sisyph · 2025-02-20T15:56:12Z

llvm/test/MC/Disassembler/AMDGPU/gfx10_vop3cx_warn.txt

@@ -0,0 +1,407 @@
+# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1010 -disassemble -show-encoding < %s 2>&1 | FileCheck -check-prefixes=GFX10 %s


Please add a RUN line with gfx11 and -mattr=+real-true16. You could use the script utils/update_mc_test_checks.py

Yes. Only gfx10 tests have been created because I want to have the code changed approved before making more tests.

For GFX10+ the destination reg of v_cmpx instructions is implicitly EXEC, which is encoded as 0x7E. However, the disassembler does not check this field, thus allowing any value. With this patch, if the field is not EXEC a warning is issued.

jwanggit86 added backend:AMDGPU mc Machine (object) code labels Feb 20, 2025

jwanggit86 requested review from jayfoad and arsenm February 20, 2025 00:33

arsenm reviewed Feb 20, 2025

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jwanggit86 linked an issue Feb 20, 2025 that may be closed by this pull request

[AMDGPU][MC][GFX10+] Warn when disassembling a VOP3 v_cmpx* opcode with dst!=EXEC #56727

Closed

Sisyph reviewed Feb 20, 2025

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jwanggit86 mentioned this pull request Feb 22, 2025

[AMDGPU][MC] Disassembler warning for v_cmpx instructions #128256

Closed

(1) Removed target generation check (2) Added comment.

76e4eb6

arsenm approved these changes Feb 26, 2025

View reviewed changes

Tests for gfx11 and gfx12.

f7988dc

arsenm approved these changes Feb 27, 2025

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jwanggit86 merged commit bc91acc into llvm:main Feb 27, 2025
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huaatian mentioned this pull request Feb 28, 2025

fix live interval empty issue huaatian/llvm-project#1

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[AMDGPU][MC] Disassembler warning for v_cmpx instructions #127925

[AMDGPU][MC] Disassembler warning for v_cmpx instructions #127925

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		@@ -0,0 +1,407 @@
		# RUN: llvm-mc -triple=amdgcn -mcpu=gfx1010 -disassemble -show-encoding < %s 2>&1 \| FileCheck -check-prefixes=GFX10 %s

[AMDGPU][MC] Disassembler warning for v_cmpx instructions #127925

[AMDGPU][MC] Disassembler warning for v_cmpx instructions #127925

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