AMDGPU: Don't use generation to determine encoding

[arsenm]

Summary

There's already a dedicated feature for this.

[scott.linder]

Sorry for the insane delay, this makes perfect sense to me.

[arsenm]

This needs to be rewritten for gfx10

[kzhuravl]

need to handle gfx10

lib/Target/AMDGPU/AMDGPUSubtarget.h

public:
   }
 
   void ParseSubtargetFeatures(StringRef CPU, StringRef FS);
 
   Generation getGeneration() const {
     return (Generation)Gen;
   }
 
+  bool isGCN3Encoding() const {
+    return GCN3Encoding;
+  }
+
   unsigned getWavefrontSizeLog2() const {
     return Log2_32(WavefrontSize);
   }
 
   int getLDSBankCount() const {
     return LDSBankCount;
   }
 

lib/Target/AMDGPU/SIInstrInfo.cpp

enum SIEncodingFamily {
   SI = 0,
   VI = 1,
   SDWA = 2,
   SDWA9 = 3,
   GFX80 = 4,
   GFX9 = 5
 };
 
-static SIEncodingFamily subtargetEncodingFamily(const GCNSubtarget &ST) {
-  switch (ST.getGeneration()) {
-  default:
-    break;
-  case AMDGPUSubtarget::SOUTHERN_ISLANDS:
-  case AMDGPUSubtarget::SEA_ISLANDS:
-    return SIEncodingFamily::SI;
-  case AMDGPUSubtarget::VOLCANIC_ISLANDS:
-  case AMDGPUSubtarget::GFX9:
-    return SIEncodingFamily::VI;
-  }
-  llvm_unreachable("Unknown subtarget generation!");
-}
-
 int SIInstrInfo::pseudoToMCOpcode(int Opcode) const {
-  SIEncodingFamily Gen = subtargetEncodingFamily(ST);
+  SIEncodingFamily Gen
+    = ST.isGCN3Encoding() ? SIEncodingFamily::VI : SIEncodingFamily::SI;
 
   if ((get(Opcode).TSFlags & SIInstrFlags::renamedInGFX9) != 0 &&
     ST.getGeneration() >= AMDGPUSubtarget::GFX9)
     Gen = SIEncodingFamily::GFX9;
 
   if (get(Opcode).TSFlags & SIInstrFlags::SDWA)
     Gen = ST.getGeneration() == AMDGPUSubtarget::GFX9 ? SIEncodingFamily::SDWA9
                                                       : SIEncodingFamily::SDWA;

test/CodeGen/AMDGPU/gcn3-encoding-feature.ll

+; RUN: llc -mtriple=amdgcn-amd-amdhsa -show-mc-encoding < %s | FileCheck %s
+
+; CHECK-LABEL: func_vi:
+; CHECK: v_add_f32_e32 v0, 1.0, v0 ; encoding: [0xf2,0x00,0x00,0x02]
+define float @func_vi(float %arg0) #1 {
+  %fadd = fadd float %arg0, 1.0
+  ret float %fadd
+}
+
+; CHECK-LABEL: func_si:
+; CHECK: v_add_f32_e32 v0, 1.0, v0 ; encoding: [0xf2,0x00,0x00,0x06]
+define float @func_si(float %arg0) #0 {
+  %fadd = fadd float %arg0, 1.0
+  ret float %fadd
+}
+
+; Defaults to SI encoding
+; CHECK-LABEL: func_unknown:
+; CHECK: v_add_f32_e32 v0, 1.0, v0 ; encoding: [0xf2,0x00,0x00,0x06]
+define float @func_unknown(float %arg0) {
+  %fadd = fadd float %arg0, 1.0
+  ret float %fadd
+}
+
+attributes #0 = { "target-features"="-gcn3-encoding" }
+attributes #1 = { "target-features"="+gcn3-encoding" }