[llvm-branch-commits] [llvm] AMDGPU: Move default wavesize hack for disassembler (PR #117422)

[Matt Arsenault via llvm-branch-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/117422

You cannot adjust the disassembler's subtarget. llvm-mc passes
the originally constructed MCSubtargetInfo around, rather than
querying the pointer in the disassembler instance.

>From bccd64648635ab9cdab25bfe3c910edc7f1adff0 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 22 Nov 2024 20:17:48 -0800
Subject: [PATCH] AMDGPU: Move default wavesize hack for disassembler

You cannot adjust the disassembler's subtarget. llvm-mc passes
the originally constructed MCSubtargetInfo around, rather than
querying the pointer in the disassembler instance.
---
 .../Disassembler/AMDGPUDisassembler.cpp       | 20 ++-----------------
 .../MCTargetDesc/AMDGPUMCTargetDesc.cpp       | 17 +++++++++++++++-
 2 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
index f90121a86c846c..7817c5ff5acc0a 100644
--- a/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
+++ b/llvm/lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
@@ -45,26 +45,10 @@ using namespace llvm;
 
 using DecodeStatus = llvm::MCDisassembler::DecodeStatus;
 
-static const MCSubtargetInfo &addDefaultWaveSize(const MCSubtargetInfo &STI,
-                                                 MCContext &Ctx) {
-  if (!STI.hasFeature(AMDGPU::FeatureWavefrontSize64) &&
-      !STI.hasFeature(AMDGPU::FeatureWavefrontSize32)) {
-    MCSubtargetInfo &STICopy = Ctx.getSubtargetCopy(STI);
-    // If there is no default wave size it must be a generation before gfx10,
-    // these have FeatureWavefrontSize64 in their definition already. For gfx10+
-    // set wave32 as a default.
-    STICopy.ToggleFeature(AMDGPU::FeatureWavefrontSize32);
-    return STICopy;
-  }
-
-  return STI;
-}
-
 AMDGPUDisassembler::AMDGPUDisassembler(const MCSubtargetInfo &STI,
                                        MCContext &Ctx, MCInstrInfo const *MCII)
-    : MCDisassembler(addDefaultWaveSize(STI, Ctx), Ctx), MCII(MCII),
-      MRI(*Ctx.getRegisterInfo()), MAI(*Ctx.getAsmInfo()),
-      TargetMaxInstBytes(MAI.getMaxInstLength(&STI)),
+    : MCDisassembler(STI, Ctx), MCII(MCII), MRI(*Ctx.getRegisterInfo()),
+      MAI(*Ctx.getAsmInfo()), TargetMaxInstBytes(MAI.getMaxInstLength(&STI)),
       CodeObjectVersion(AMDGPU::getDefaultAMDHSACodeObjectVersion()) {
   // ToDo: AMDGPUDisassembler supports only VI ISA.
   if (!STI.hasFeature(AMDGPU::FeatureGCN3Encoding) && !isGFX10Plus())
diff --git a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp
index 29be64625811f7..c692895d84c002 100644
--- a/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp
+++ b/llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUMCTargetDesc.cpp
@@ -77,7 +77,22 @@ static MCSubtargetInfo *
 createAMDGPUMCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef FS) {
   if (TT.getArch() == Triple::r600)
     return createR600MCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
-  return createAMDGPUMCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
+
+  MCSubtargetInfo *STI =
+      createAMDGPUMCSubtargetInfoImpl(TT, CPU, /*TuneCPU*/ CPU, FS);
+
+  // FIXME: We should error for the default target.
+  if (!STI->hasFeature(AMDGPU::FeatureWavefrontSize64) &&
+      !STI->hasFeature(AMDGPU::FeatureWavefrontSize32)) {
+    // If there is no default wave size it must be a generation before gfx10,
+    // these have FeatureWavefrontSize64 in their definition already. For gfx10+
+    // set wave32 as a default.
+    STI->ToggleFeature(AMDGPU::isGFX10Plus(*STI)
+                           ? AMDGPU::FeatureWavefrontSize32
+                           : AMDGPU::FeatureWavefrontSize64);
+  }
+
+  return STI;
 }
 
 static MCInstPrinter *createAMDGPUMCInstPrinter(const Triple &T,