AMDGPU: Handle cvt_scale F32/F16->F4/F8 gfx950 hazard (llvm#117844)

gfx950 SP changes doc says:
No 4 clk forwarding on opcodes that convert from
F32/F16->F8 or F32/F16->F4. Must insert a NOP or
instruction writing some other destination VREG
after a conversion to F4/F8 since it writes either
low/high half or bytes.

Co-authored-by: Pravin Jagtap <[email protected]>
Co-authored-by: Jeffrey Byrnes <[email protected]>

Author: 3 people

llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp

@@ -907,17 +907,18 @@ getDstSelForwardingOperand(const MachineInstr &MI, const GCNSubtarget &ST) {
 
   // There are three different types of instructions
   // which produce forwarded dest: 1. SDWA with dst_sel != DWORD, 2. VOP3
-  // which write hi bits (e.g. op_sel[3] == 1), and 3. CVR_SR_FP8_F32 and
-  // CVT_SR_BF8_F32 with op_sel[3:2]
+  // which write hi bits (e.g. op_sel[3] == 1), and 3. FP8DstSelInst
+  // (instructions with dest byte sel, e.g. CVT_SR_BF8_F32) and
+  // op_sel[3:2]
   // != 0
   if (SIInstrInfo::isSDWA(MI)) {
     // Type 1: SDWA with dst_sel != DWORD
     if (auto *DstSel = TII->getNamedOperand(MI, AMDGPU::OpName::dst_sel))
       if (DstSel->getImm() == AMDGPU::SDWA::DWORD)
         return nullptr;
   } else {
-    // Type 2 && Type 3: (VOP3 which write the hi bits) || (CVT_SR_FP8_F32 and
-    // CVT_SR_BF8_F32 with op_sel[3:2] != 0)
+    // Type 2 && Type 3: (VOP3 which write the hi bits) || (FP8DstSelInst
+    // with op_sel[3:2] != 0)
     if (!AMDGPU::hasNamedOperand(Opcode, AMDGPU::OpName::op_sel) ||
         !(TII->getNamedOperand(MI, AMDGPU::OpName::src0_modifiers)->getImm() &
               SISrcMods::DST_OP_SEL ||
@@ -981,7 +982,7 @@ int GCNHazardRecognizer::checkVALUHazards(MachineInstr *VALU) {
     WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForDef);
   }
 
-  if (ST.hasDstSelForwardingHazard()) {
+  if (ST.hasDstSelForwardingHazard() || ST.hasCvtScaleForwardingHazard()) {
     const int Shift16DefWaitstates = 1;
 
     auto IsShift16BitDefFn = [this, VALU](const MachineInstr &ProducerMI) {
@@ -1092,7 +1093,8 @@ int GCNHazardRecognizer::checkInlineAsmHazards(MachineInstr *IA) {
   // problematic thus far.
 
   // see checkVALUHazards()
-  if (!ST.has12DWordStoreHazard() && !ST.hasDstSelForwardingHazard())
+  if (!ST.has12DWordStoreHazard() && !ST.hasDstSelForwardingHazard() &&
+      !ST.hasCvtScaleForwardingHazard())
     return 0;
 
   const MachineRegisterInfo &MRI = MF.getRegInfo();

llvm/lib/Target/AMDGPU/GCNSubtarget.h

@@ -1265,6 +1265,8 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
 
   bool hasVALUTransUseHazard() const { return HasVALUTransUseHazard; }
 
+  bool hasCvtScaleForwardingHazard() const { return GFX950Insts; }
+
   bool hasForceStoreSC0SC1() const { return HasForceStoreSC0SC1; }
 
   bool requiresCodeObjectV6() const { return RequiresCOV6; }

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

@@ -385,6 +385,14 @@ struct SingleUseExceptionInfo {
   bool IsInvalidSingleUseProducer;
 };
 
+#define GET_FP8DstByteSelTable_DECL
+#define GET_FP8DstByteSelTable_IMPL
+
+struct DPMACCInstructionInfo {
+  uint16_t Opcode;
+  bool IsDPMACCInstruction;
+};
+
 struct FP8DstByteSelInfo {
   uint16_t Opcode;
   bool HasFP8DstByteSel;
@@ -427,6 +435,8 @@ struct FP8DstByteSelInfo {
 #define GET_getMFMA_F8F6F4_WithSize_DECL
 #define GET_getMFMA_F8F6F4_WithSize_IMPL
 #define GET_isMFMA_F8F6F4Table_IMPL
+#define GET_isCvtScaleF32_F32F16ToF8F4Table_IMPL
+
 #include "AMDGPUGenSearchableTables.inc"
 
 int getMTBUFBaseOpcode(unsigned Opc) {

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

@@ -103,6 +103,10 @@ struct MFMA_F8F6F4_Info {
   uint8_t NumRegsSrcB;
 };
 
+struct CvtScaleF32_F32F16ToF8F4_Info {
+  unsigned Opcode;
+};
+
 #define GET_MIMGBaseOpcode_DECL
 #define GET_MIMGDim_DECL
 #define GET_MIMGEncoding_DECL
@@ -112,6 +116,7 @@ struct MFMA_F8F6F4_Info {
 #define GET_MAIInstInfoTable_DECL
 #define GET_MAIInstInfoTable_DECL
 #define GET_isMFMA_F8F6F4Table_DECL
+#define GET_isCvtScaleF32_F32F16ToF8F4Table_DECL
 #include "AMDGPUGenSearchableTables.inc"
 
 namespace IsaInfo {

llvm/lib/Target/AMDGPU/VOP3Instructions.td

@@ -973,11 +973,16 @@ class VOP3_CVT_SCALE_FP4FP8BF8_F32_TiedInput_Profile<VOPProfile P> : VOP3_Profil
   let HasOMod = 0;
 }
 
+class VOP3_CVT_SCALE_FP4_F32_TiedInput_Profile<VOPProfile P> : VOP3_CVT_SCALE_FP4FP8BF8_F32_TiedInput_Profile<P> {
+  let HasFP8DstByteSel = 1;
+}
+
 class VOP3_CVT_SCALE_SR_F8BF8_F16BF16F32_TiedInput_Profile<VOPProfile P> : VOP3_CVT_SCALE_FP4FP8BF8_F32_TiedInput_Profile<P> {
   let InsVOP3OpSel = (ins FP32InputMods:$src0_modifiers, Src0RC64:$src0,
                           Int32InputMods:$src1_modifiers, Src1RC64:$src1,
                           FP32InputMods:$src2_modifiers, Src2RC64:$src2,
                           VGPR_32:$vdst_in, op_sel0:$op_sel);
+  let HasFP8DstByteSel = 1;
 }
 
 
@@ -995,6 +1000,7 @@ class VOP3_CVT_SCALE_FP4_F16BF16_TiedInput_Profile<VOPProfile P> : VOP3_Profile<
                                             HasSrc0FloatMods, HasSrc1FloatMods,
                                             HasSrc2FloatMods>.ret);
   let HasExtVOP3DPP = 0;
+  let HasFP8DstByteSel = 1;
 }
 
 class VOP3_CVT_SCALE_SR_PK_F4_F16BF16_TiedInput_Profile<ValueType Src0Ty> :
@@ -1007,6 +1013,7 @@ class VOP3_CVT_SCALE_SR_PK_F4_F16BF16_TiedInput_Profile<ValueType Src0Ty> :
   let HasExtVOP3DPP = 0;
   let HasOpSel = 1;
   let HasOMod = 0;
+  let HasFP8DstByteSel = 1;
 }
 
 def VOP3_CVT_SCALE_SR_PK_F4_F32_TiedInput_Profile : VOP3_Profile<VOPProfile<[i32, v2f32, i32, f32]>, VOP3_OPSEL> {
@@ -1018,6 +1025,7 @@ def VOP3_CVT_SCALE_SR_PK_F4_F32_TiedInput_Profile : VOP3_Profile<VOPProfile<[i32
   let HasExtVOP3DPP = 0;
   let HasOpSel = 1;
   let HasOMod = 0;
+  let HasFP8DstByteSel = 1;
 }
 
 class VOP3_CVT_SCALE_PK_F16BF16F32_FP4FP8BF8_Profile<ValueType DstTy> : VOP3_Profile<VOPProfile<[DstTy, i32, f32, untyped]>,
@@ -1093,7 +1101,7 @@ let SubtargetPredicate = HasBF8ConversionScaleInsts, mayRaiseFPException = 0 in
 let SubtargetPredicate = HasFP4ConversionScaleInsts, mayRaiseFPException = 0 in {
   defm V_CVT_SCALEF32_PK_F32_FP4 : VOP3Inst<"v_cvt_scalef32_pk_f32_fp4", VOP3_CVT_SCALE_PK_F16BF16F32_FP4FP8BF8_Profile<v2f32>>;
   let Constraints = "$vdst = $vdst_in", DisableEncoding="$vdst_in" in {
-    defm V_CVT_SCALEF32_PK_FP4_F32 : VOP3Inst<"v_cvt_scalef32_pk_fp4_f32", VOP3_CVT_SCALE_FP4FP8BF8_F32_TiedInput_Profile<VOP_I32_F32_F32_F32>>;
+    defm V_CVT_SCALEF32_PK_FP4_F32 : VOP3Inst<"v_cvt_scalef32_pk_fp4_f32", VOP3_CVT_SCALE_FP4_F32_TiedInput_Profile<VOP_I32_F32_F32_F32>>;
     let Constraints = "@earlyclobber $vdst" in {
       defm V_CVT_SCALEF32_SR_PK_FP4_F16:  VOP3Inst<"v_cvt_scalef32_sr_pk_fp4_f16", VOP3_CVT_SCALE_SR_PK_F4_F16BF16_TiedInput_Profile<v2f16>>;
       defm V_CVT_SCALEF32_SR_PK_FP4_BF16: VOP3Inst<"v_cvt_scalef32_sr_pk_fp4_bf16", VOP3_CVT_SCALE_SR_PK_F4_F16BF16_TiedInput_Profile<v2bf16>>;
@@ -2027,6 +2035,7 @@ multiclass VOP3_Real_BITOP3_gfx9<bits<10> op, string AsmName, bit isSingle = 0>
     }
   }
 }
+
 } // End AssemblerPredicate = isGFX9Only, DecoderNamespace = "GFX9"
 
 defm V_MAD_U64_U32      : VOP3be_Real_vi <0x1E8>;