[llvm] [AMDGPU] Allow unaligned VGPR for ds_read_b96_tr_b6 (PR #125169)

[Pravin Jagtap via llvm-commits]

https://github.com/pravinjagtap created https://github.com/llvm/llvm-project/pull/125169

All load transpose instructions follow gfx950 standard of even aligned VGPR except ds_read_b96_tr_b6, which allows unaligned VGPR.

>From 035fa4f2c9c1823504a26560e96d0ab0486e2a80 Mon Sep 17 00:00:00 2001
From: Pravin Jagtap <Pravin.Jagtap at amd.com>
Date: Fri, 31 Jan 2025 10:33:31 +0530
Subject: [PATCH] [AMDGPU] Allow unaligned VGPR for ds_read_b96_tr_b6

All load transpose instructions follow gfx950 standard of
even aligned VGPR except ds_read_b96_tr_b6, which allows
unaligned VGPR.
---
 llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp      | 5 ++++-
 llvm/test/MC/AMDGPU/gfx950-unsupported.s                  | 4 ----
 llvm/test/MC/AMDGPU/gfx950_asm_read_tr.s                  | 8 ++++++++
 .../MC/Disassembler/AMDGPU/gfx950_dasm_ds_read_tr.txt     | 6 ++++++
 4 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
index d8f441d1ccfe44..ed922245b3e2ba 100644
--- a/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
+++ b/llvm/lib/Target/AMDGPU/AsmParser/AMDGPUAsmParser.cpp
@@ -4853,7 +4853,10 @@ bool AMDGPUAsmParser::validateAGPRLdSt(const MCInst &Inst) const {
 
 bool AMDGPUAsmParser::validateVGPRAlign(const MCInst &Inst) const {
   auto FB = getFeatureBits();
-  if (!FB[AMDGPU::FeatureGFX90AInsts])
+  unsigned Opc = Inst.getOpcode();
+  // DS_READ_B96_TR_B6 is the only DS instruction in GFX950, that allows
+  // unaligned VGPR. All others only allow even aligned VGPRs.
+  if (!(FB[AMDGPU::FeatureGFX90AInsts]) || Opc == AMDGPU::DS_READ_B96_TR_B6_vi)
     return true;
 
   const MCRegisterInfo *MRI = getMRI();
diff --git a/llvm/test/MC/AMDGPU/gfx950-unsupported.s b/llvm/test/MC/AMDGPU/gfx950-unsupported.s
index 225784177ae185..8bdab2da2394cc 100644
--- a/llvm/test/MC/AMDGPU/gfx950-unsupported.s
+++ b/llvm/test/MC/AMDGPU/gfx950-unsupported.s
@@ -239,10 +239,6 @@ ds_read_b64_tr_b16 v[2:3], v2 offset:-64
 //===----------------------------------------------------------------------===//
 // ds_read_b96_tr_b6
 //===----------------------------------------------------------------------===//
-ds_read_b96_tr_b6 v[1:3], v0
-// ERR: :[[@LINE-1]]:{{[0-9]+}}: error: invalid register class: vgpr tuples must be 64 bit aligned
-// W32-ERR: :[[@LINE-2]]:{{[0-9]+}}: error: instruction not supported on this GPU
-
 ds_read_b96_tr_b6 v1, v0
 // ERR: :[[@LINE-1]]:{{[0-9]+}}: error: invalid operand for instruction
 // W32-ERR: :[[@LINE-2]]:{{[0-9]+}}: error: instruction not supported on this GPU
diff --git a/llvm/test/MC/AMDGPU/gfx950_asm_read_tr.s b/llvm/test/MC/AMDGPU/gfx950_asm_read_tr.s
index a6907caafcbb61..b9ceb143ecf8e8 100644
--- a/llvm/test/MC/AMDGPU/gfx950_asm_read_tr.s
+++ b/llvm/test/MC/AMDGPU/gfx950_asm_read_tr.s
@@ -32,3 +32,11 @@ ds_read_b96_tr_b6 v[0:2], v0
 ds_read_b96_tr_b6 v[2:4], v2 offset:64
 // GFX940-ERR: [[@LINE-1]]:{{[0-9]+}}: error: instruction not supported on this GPU
 // GFX950: encoding: [0x40,0x00,0xc2,0xd9,0x02,0x00,0x00,0x02]
+
+ds_read_b96_tr_b6 v[1:3], v0
+// GFX940-ERR: [[@LINE-1]]:{{[0-9]+}}: error: instruction not supported on this GPU
+// GFX950: encoding: [0x00,0x00,0xc2,0xd9,0x00,0x00,0x00,0x01]
+
+ds_read_b96_tr_b6 v[1:3], v2 offset:64
+// GFX940-ERR: [[@LINE-1]]:{{[0-9]+}}: error: instruction not supported on this GPU
+// GFX950: encoding: [0x40,0x00,0xc2,0xd9,0x02,0x00,0x00,0x01]
\ No newline at end of file
diff --git a/llvm/test/MC/Disassembler/AMDGPU/gfx950_dasm_ds_read_tr.txt b/llvm/test/MC/Disassembler/AMDGPU/gfx950_dasm_ds_read_tr.txt
index 10310f7ad1f3de..0b5dba24612ca5 100644
--- a/llvm/test/MC/Disassembler/AMDGPU/gfx950_dasm_ds_read_tr.txt
+++ b/llvm/test/MC/Disassembler/AMDGPU/gfx950_dasm_ds_read_tr.txt
@@ -35,3 +35,9 @@
 
 # GFX950: ds_read_b96_tr_b6 v[2:4], v2 offset:64  ; encoding: [0x40,0x00,0xc2,0xd9,0x02,0x00,0x00,0x02]
 0x40,0x00,0xc2,0xd9,0x02,0x00,0x00,0x02
+
+# GFX950: ds_read_b96_tr_b6 v[1:3], v0            ; encoding: [0x00,0x00,0xc2,0xd9,0x00,0x00,0x00,0x01]
+0x00,0x00,0xc2,0xd9,0x00,0x00,0x00,0x01
+
+# GFX950: ds_read_b96_tr_b6 v[1:3], v2 offset:64  ; encoding: [0x40,0x00,0xc2,0xd9,0x02,0x00,0x00,0x01]
+0x40,0x00,0xc2,0xd9,0x02,0x00,0x00,0x01