AMDGPU/GlobalISel: Disable LCSSA pass

Disable LCSSA pass in preparation for implementing temporal divergence lowering in amdgpu divergence lowering. Breaks all cases where sgpr or i1 values are used outside of the cycle with divergent exit. Regenerate regression tests for amdgpu divergence lowering with LCSSA disabled and switch them to new reg bank select. Also add required regbanklegalize rules for these tests to pass. Update IntrinsicLaneMaskAnalyzer to stop tracking lcssa phis that are lane masks.
llvm · Feb 24, 2025 · 11a9bd2 · 11a9bd2
1 parent f1252f5
commit 11a9bd2
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Showing 20 changed files with 2,662 additions and 1,562 deletions.
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.cpp b/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.cpp
@@ -91,25 +91,17 @@ void IntrinsicLaneMaskAnalyzer::initLaneMaskIntrinsics(MachineFunction &MF) {
       GIntrinsic *GI = dyn_cast<GIntrinsic>(&MI);
       if (GI && GI->is(Intrinsic::amdgcn_if_break)) {
         S32S64LaneMask.insert(MI.getOperand(3).getReg());
-        findLCSSAPhi(MI.getOperand(0).getReg());
+        S32S64LaneMask.insert(MI.getOperand(0).getReg());
       }
 
       if (MI.getOpcode() == AMDGPU::SI_IF ||
           MI.getOpcode() == AMDGPU::SI_ELSE) {
-        findLCSSAPhi(MI.getOperand(0).getReg());
+        S32S64LaneMask.insert(MI.getOperand(0).getReg());
       }
     }
   }
 }
 
-void IntrinsicLaneMaskAnalyzer::findLCSSAPhi(Register Reg) {
-  S32S64LaneMask.insert(Reg);
-  for (const MachineInstr &LCSSAPhi : MRI.use_instructions(Reg)) {
-    if (LCSSAPhi.isPHI())
-      S32S64LaneMask.insert(LCSSAPhi.getOperand(0).getReg());
-  }
-}
-
 static LLT getReadAnyLaneSplitTy(LLT Ty) {
   if (Ty.isVector()) {
     LLT ElTy = Ty.getElementType();

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.h b/llvm/lib/Target/AMDGPU/AMDGPUGlobalISelUtils.h
@@ -47,8 +47,6 @@ class IntrinsicLaneMaskAnalyzer {
 
 private:
   void initLaneMaskIntrinsics(MachineFunction &MF);
-  // This will not be needed when we turn off LCSSA for global-isel.
-  void findLCSSAPhi(Register Reg);
 };
 
 void buildReadAnyLane(MachineIRBuilder &B, Register SgprDst, Register VgprSrc,

diff --git a/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalize.cpp b/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalize.cpp
@@ -312,6 +312,12 @@ bool AMDGPURegBankLegalize::runOnMachineFunction(MachineFunction &MF) {
     }
 
     // Opcodes that also support S1.
+    if (Opc == G_FREEZE &&
+        MRI.getType(MI->getOperand(0).getReg()) != LLT::scalar(1)) {
+      RBLHelper.applyMappingTrivial(*MI);
+      continue;
+    }
+
     if ((Opc == AMDGPU::G_CONSTANT || Opc == AMDGPU::G_FCONSTANT ||
          Opc == AMDGPU::G_IMPLICIT_DEF)) {
       Register Dst = MI->getOperand(0).getReg();

diff --git a/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalizeHelper.cpp b/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalizeHelper.cpp
@@ -134,6 +134,26 @@ void RegBankLegalizeHelper::lower(MachineInstr &MI,
   switch (Mapping.LoweringMethod) {
   case DoNotLower:
     return;
+  case VccExtToSel: {
+    LLT Ty = MRI.getType(MI.getOperand(0).getReg());
+    Register Src = MI.getOperand(1).getReg();
+    unsigned Opc = MI.getOpcode();
+    if (Ty == S32 || Ty == S16) {
+      auto True = B.buildConstant({VgprRB, Ty}, Opc == G_SEXT ? -1 : 1);
+      auto False = B.buildConstant({VgprRB, Ty}, 0);
+      B.buildSelect(MI.getOperand(0).getReg(), Src, True, False);
+    }
+    if (Ty == S64) {
+      auto True = B.buildConstant({VgprRB, S32}, Opc == G_SEXT ? -1 : 1);
+      auto False = B.buildConstant({VgprRB, S32}, 0);
+      auto Sel = B.buildSelect({VgprRB, S32}, Src, True, False);
+      B.buildMergeValues(
+          MI.getOperand(0).getReg(),
+          {Sel.getReg(0), Opc == G_SEXT ? Sel.getReg(0) : False.getReg(0)});
+    }
+    MI.eraseFromParent();
+    return;
+  }
   case UniExtToSel: {
     LLT Ty = MRI.getType(MI.getOperand(0).getReg());
     auto True = B.buildConstant({SgprRB, Ty},
@@ -276,6 +296,8 @@ LLT RegBankLegalizeHelper::getTyFromID(RegBankLLTMappingApplyID ID) {
   case Sgpr64:
   case Vgpr64:
     return LLT::scalar(64);
+  case VgprP0:
+    return LLT::pointer(0, 64);
   case SgprP1:
   case VgprP1:
     return LLT::pointer(1, 64);
@@ -383,6 +405,7 @@ RegBankLegalizeHelper::getRegBankFromID(RegBankLLTMappingApplyID ID) {
     return SgprRB;
   case Vgpr32:
   case Vgpr64:
+  case VgprP0:
   case VgprP1:
   case VgprP3:
   case VgprP4:
@@ -425,6 +448,7 @@ void RegBankLegalizeHelper::applyMappingDst(
     case SgprV4S32:
     case Vgpr32:
     case Vgpr64:
+    case VgprP0:
     case VgprP1:
     case VgprP3:
     case VgprP4:
@@ -555,6 +579,7 @@ void RegBankLegalizeHelper::applyMappingSrc(
     // vgpr scalars, pointers and vectors
     case Vgpr32:
     case Vgpr64:
+    case VgprP0:
     case VgprP1:
     case VgprP3:
     case VgprP4:
@@ -653,7 +678,8 @@ void RegBankLegalizeHelper::applyMappingPHI(MachineInstr &MI) {
   // We accept all types that can fit in some register class.
   // Uniform G_PHIs have all sgpr registers.
   // Divergent G_PHIs have vgpr dst but inputs can be sgpr or vgpr.
-  if (Ty == LLT::scalar(32) || Ty == LLT::pointer(4, 64)) {
+  if (Ty == LLT::scalar(32) || Ty == LLT::pointer(1, 64) ||
+      Ty == LLT::pointer(4, 64)) {
     return;
   }
 

diff --git a/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalizeRules.cpp b/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalizeRules.cpp
@@ -50,6 +50,8 @@ bool matchUniformityAndLLT(Register Reg, UniformityLLTOpPredicateID UniID,
     return MRI.getType(Reg) == LLT::scalar(32);
   case S64:
     return MRI.getType(Reg) == LLT::scalar(64);
+  case P0:
+    return MRI.getType(Reg) == LLT::pointer(0, 64);
   case P1:
     return MRI.getType(Reg) == LLT::pointer(1, 64);
   case P3:
@@ -58,6 +60,8 @@ bool matchUniformityAndLLT(Register Reg, UniformityLLTOpPredicateID UniID,
     return MRI.getType(Reg) == LLT::pointer(4, 64);
   case P5:
     return MRI.getType(Reg) == LLT::pointer(5, 32);
+  case V4S32:
+    return MRI.getType(Reg) == LLT::fixed_vector(4, 32);
   case B32:
     return MRI.getType(Reg).getSizeInBits() == 32;
   case B64:
@@ -78,6 +82,8 @@ bool matchUniformityAndLLT(Register Reg, UniformityLLTOpPredicateID UniID,
     return MRI.getType(Reg) == LLT::scalar(32) && MUI.isUniform(Reg);
   case UniS64:
     return MRI.getType(Reg) == LLT::scalar(64) && MUI.isUniform(Reg);
+  case UniP0:
+    return MRI.getType(Reg) == LLT::pointer(0, 64) && MUI.isUniform(Reg);
   case UniP1:
     return MRI.getType(Reg) == LLT::pointer(1, 64) && MUI.isUniform(Reg);
   case UniP3:
@@ -104,6 +110,8 @@ bool matchUniformityAndLLT(Register Reg, UniformityLLTOpPredicateID UniID,
     return MRI.getType(Reg) == LLT::scalar(32) && MUI.isDivergent(Reg);
   case DivS64:
     return MRI.getType(Reg) == LLT::scalar(64) && MUI.isDivergent(Reg);
+  case DivP0:
+    return MRI.getType(Reg) == LLT::pointer(0, 64) && MUI.isDivergent(Reg);
   case DivP1:
     return MRI.getType(Reg) == LLT::pointer(1, 64) && MUI.isDivergent(Reg);
   case DivP3:
@@ -315,13 +323,15 @@ RegBankLegalizeRules::getRulesForOpc(MachineInstr &MI) const {
       Opc == AMDGPU::G_INTRINSIC_CONVERGENT_W_SIDE_EFFECTS) {
     unsigned IntrID = cast<GIntrinsic>(MI).getIntrinsicID();
     if (!IRulesAlias.contains(IntrID)) {
+      MI.dump();
       LLVM_DEBUG(dbgs() << "MI: "; MI.dump(););
       llvm_unreachable("No rules defined for intrinsic opcode");
     }
     return IRules.at(IRulesAlias.at(IntrID));
   }
 
   if (!GRulesAlias.contains(Opc)) {
+    MI.dump();
     LLVM_DEBUG(dbgs() << "MI: "; MI.dump(););
     llvm_unreachable("No rules defined for generic opcode");
   }
@@ -431,16 +441,21 @@ RegBankLegalizeRules::RegBankLegalizeRules(const GCNSubtarget &_ST,
   addRulesForGOpcs({G_XOR, G_OR, G_AND}, StandardB)
       .Any({{UniS1}, {{Sgpr32Trunc}, {Sgpr32AExt, Sgpr32AExt}}})
       .Any({{DivS1}, {{Vcc}, {Vcc, Vcc}}})
+      .Div(B32, {{VgprB32}, {VgprB32, VgprB32}})
+      .Uni(B64, {{SgprB64}, {SgprB64, SgprB64}})
       .Div(B64, {{VgprB64}, {VgprB64, VgprB64}, SplitTo32});
 
   addRulesForGOpcs({G_SHL}, Standard)
+      .Div(S32, {{Vgpr32}, {Vgpr32, Vgpr32}})
       .Uni(S64, {{Sgpr64}, {Sgpr64, Sgpr32}})
       .Div(S64, {{Vgpr64}, {Vgpr64, Vgpr32}});
 
   // Note: we only write S1 rules for G_IMPLICIT_DEF, G_CONSTANT, G_FCONSTANT
   // and G_FREEZE here, rest is trivially regbankselected earlier
+  addRulesForGOpcs({G_IMPLICIT_DEF}).Any({{UniS1}, {{Sgpr32Trunc}, {}}});
   addRulesForGOpcs({G_CONSTANT})
       .Any({{UniS1, _}, {{Sgpr32Trunc}, {None}, UniCstExt}});
+  addRulesForGOpcs({G_FREEZE}).Any({{DivS1}, {{Vcc}, {Vcc}}});
 
   addRulesForGOpcs({G_ICMP})
       .Any({{UniS1, _, S32}, {{Sgpr32Trunc}, {None, Sgpr32, Sgpr32}}})
@@ -471,6 +486,7 @@ RegBankLegalizeRules::RegBankLegalizeRules(const GCNSubtarget &_ST,
 
   addRulesForGOpcs({G_ZEXT, G_SEXT})
       .Any({{UniS32, S1}, {{Sgpr32}, {Sgpr32AExtBoolInReg}, UniExtToSel}})
+      .Any({{DivS32, S1}, {{Vgpr32}, {Vcc}, VccExtToSel}})
       .Any({{UniS64, S32}, {{Sgpr64}, {Sgpr32}, Ext32To64}})
       .Any({{DivS64, S32}, {{Vgpr64}, {Vgpr32}, Ext32To64}});
 
@@ -525,9 +541,12 @@ RegBankLegalizeRules::RegBankLegalizeRules(const GCNSubtarget &_ST,
 
   // clang-format off
   addRulesForGOpcs({G_LOAD})
+      .Any({{DivB32, DivP0}, {{VgprB32}, {VgprP0}}})
+
       .Any({{DivB32, DivP1}, {{VgprB32}, {VgprP1}}})
       .Any({{{UniB256, UniP1}, isAlign4 && isUL}, {{SgprB256}, {SgprP1}}})
       .Any({{{UniB512, UniP1}, isAlign4 && isUL}, {{SgprB512}, {SgprP1}}})
+      .Any({{{UniB32, UniP1}, !isAlign4 || !isUL}, {{UniInVgprB32}, {SgprP1}}})
       .Any({{{UniB256, UniP1}, !isAlign4 || !isUL}, {{UniInVgprB256}, {VgprP1}, SplitLoad}})
       .Any({{{UniB512, UniP1}, !isAlign4 || !isUL}, {{UniInVgprB512}, {VgprP1}, SplitLoad}})
 
@@ -556,15 +575,26 @@ RegBankLegalizeRules::RegBankLegalizeRules(const GCNSubtarget &_ST,
   // clang-format on
 
   addRulesForGOpcs({G_AMDGPU_BUFFER_LOAD}, Vector)
+      .Div(S32, {{Vgpr32}, {SgprV4S32, Vgpr32, Vgpr32, Sgpr32}})
+      .Uni(S32, {{UniInVgprS32}, {SgprV4S32, Vgpr32, Vgpr32, Sgpr32}})
       .Div(V4S32, {{VgprV4S32}, {SgprV4S32, Vgpr32, Vgpr32, Sgpr32}})
       .Uni(V4S32, {{UniInVgprV4S32}, {SgprV4S32, Vgpr32, Vgpr32, Sgpr32}});
 
   addRulesForGOpcs({G_STORE})
+      .Any({{S32, P0}, {{}, {Vgpr32, VgprP0}}})
       .Any({{S32, P1}, {{}, {Vgpr32, VgprP1}}})
       .Any({{S64, P1}, {{}, {Vgpr64, VgprP1}}})
       .Any({{V4S32, P1}, {{}, {VgprV4S32, VgprP1}}});
 
-  addRulesForGOpcs({G_PTR_ADD}).Any({{DivP1}, {{VgprP1}, {VgprP1, Vgpr64}}});
+  addRulesForGOpcs({G_AMDGPU_BUFFER_STORE})
+      .Any({{S32}, {{}, {Vgpr32, SgprV4S32, Vgpr32, Vgpr32, Sgpr32}}});
+
+  addRulesForGOpcs({G_PTR_ADD})
+      .Any({{UniP1}, {{SgprP1}, {SgprP1, Sgpr64}}})
+      .Any({{DivP1}, {{VgprP1}, {VgprP1, Vgpr64}}})
+      .Any({{DivP0}, {{VgprP0}, {VgprP0, Vgpr64}}});
+
+  addRulesForGOpcs({G_INTTOPTR}).Any({{UniP4}, {{SgprP4}, {Sgpr64}}});
 
   addRulesForGOpcs({G_ABS}, Standard).Uni(S16, {{Sgpr32Trunc}, {Sgpr32SExt}});
 
@@ -580,15 +610,24 @@ RegBankLegalizeRules::RegBankLegalizeRules(const GCNSubtarget &_ST,
       .Any({{UniS32, S32}, {{UniInVgprS32}, {Vgpr32}}}, !hasSALUFloat);
 
   addRulesForGOpcs({G_UITOFP})
+      .Any({{DivS32, S32}, {{Vgpr32}, {Vgpr32}}})
       .Any({{UniS32, S32}, {{Sgpr32}, {Sgpr32}}}, hasSALUFloat)
       .Any({{UniS32, S32}, {{UniInVgprS32}, {Vgpr32}}}, !hasSALUFloat);
 
   using namespace Intrinsic;
 
+  addRulesForIOpcs({amdgcn_s_getpc}).Any({{UniS64, _}, {{Sgpr64}, {None}}});
+
   // This is "intrinsic lane mask" it was set to i32/i64 in llvm-ir.
   addRulesForIOpcs({amdgcn_end_cf}).Any({{_, S32}, {{}, {None, Sgpr32}}});
 
   addRulesForIOpcs({amdgcn_if_break}, Standard)
       .Uni(S32, {{Sgpr32}, {IntrId, Vcc, Sgpr32}});
 
+  addRulesForIOpcs({amdgcn_mbcnt_lo, amdgcn_mbcnt_hi}, Standard)
+      .Div(S32, {{}, {Vgpr32, None, Vgpr32, Vgpr32}});
+
+  addRulesForIOpcs({amdgcn_readfirstlane})
+      .Any({{UniS32, _, DivS32}, {{}, {Sgpr32, None, Vgpr32}}});
+
 } // end initialize rules
diff --git a/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalizeRules.h b/llvm/lib/Target/AMDGPU/AMDGPURegBankLegalizeRules.h
@@ -50,16 +50,19 @@ enum UniformityLLTOpPredicateID {
   DivS64,
 
   // pointers
+  P0,
   P1,
   P3,
   P4,
   P5,
 
+  UniP0,
   UniP1,
   UniP3,
   UniP4,
   UniP5,
 
+  DivP0,
   DivP1,
   DivP3,
   DivP4,
@@ -124,6 +127,7 @@ enum RegBankLLTMappingApplyID {
   // vgpr scalars, pointers, vectors and B-types
   Vgpr32,
   Vgpr64,
+  VgprP0,
   VgprP1,
   VgprP3,
   VgprP4,
@@ -162,6 +166,7 @@ enum RegBankLLTMappingApplyID {
 // vgpr. Lower it to two S32 vgpr ANDs.
 enum LoweringMethodID {
   DoNotLower,
+  VccExtToSel,
   UniExtToSel,
   VgprToVccCopy,
   SplitTo32,

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.cpp
@@ -1382,7 +1382,11 @@ bool GCNPassConfig::addPreISel() {
   // control flow modifications.
   addPass(createAMDGPURewriteUndefForPHILegacyPass());
 
-  addPass(createLCSSAPass());
+  // SDAG requires LCSSA, GlobalISel does not. Disable LCSSA for -global-isel
+  // with -new-reg-bank-select and without any of the fallback options.
+  if (!getCGPassBuilderOption().EnableGlobalISelOption ||
+      !isGlobalISelAbortEnabled() || !NewRegBankSelect)
+    addPass(createLCSSAPass());
 
   if (TM->getOptLevel() > CodeGenOptLevel::Less)
     addPass(&AMDGPUPerfHintAnalysisLegacyID);
@@ -2086,7 +2090,9 @@ void AMDGPUCodeGenPassBuilder::addPreISel(AddIRPass &addPass) const {
   // control flow modifications.
   addPass(AMDGPURewriteUndefForPHIPass());
 
-  addPass(LCSSAPass());
+  if (!getCGPassBuilderOption().EnableGlobalISelOption ||
+      !isGlobalISelAbortEnabled() || !NewRegBankSelect)
+    addPass(LCSSAPass());
 
   if (TM.getOptLevel() > CodeGenOptLevel::Less)
     addPass(AMDGPUPerfHintAnalysisPass(TM));