[GlobalISel][ARM] Legalization of G_CONSTANT using constant pool

llvm/lib/Target/ARM/ARMInstructionSelector.cpp

@@ -14,6 +14,7 @@
 #include "ARMSubtarget.h"
 #include "ARMTargetMachine.h"
 #include "llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h"
+#include "llvm/CodeGen/GlobalISel/GenericMachineInstrs.h"
 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
 #include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -1088,7 +1089,7 @@ bool ARMInstructionSelector::select(MachineInstr &I) {
     return selectGlobal(MIB, MRI);
   case G_STORE:
   case G_LOAD: {
-    const auto &MemOp = **I.memoperands_begin();
+    auto &MemOp = **I.memoperands_begin();
     if (MemOp.isAtomic()) {
       LLVM_DEBUG(dbgs() << "Atomic load/store not supported yet\n");
       return false;
@@ -1103,6 +1104,26 @@ bool ARMInstructionSelector::select(MachineInstr &I) {
     assert((ValSize != 64 || STI.hasVFP2Base()) &&
            "Don't know how to load/store 64-bit value without VFP");
 
+    if (auto *LoadMI = dyn_cast<GLoad>(&I)) {
+      Register PtrReg = LoadMI->getPointerReg();
+      MachineInstr *Ptr = MRI.getVRegDef(PtrReg);
+      if (Ptr->getOpcode() == TargetOpcode::G_CONSTANT_POOL) {
+        const MachineOperand &Index = Ptr->getOperand(1);
+        unsigned Opcode = Subtarget->isThumb() ? ARM::tLDRpci : ARM::LDRcp;
+
+        auto Instr = BuildMI(MBB, I, I.getDebugLoc(), TII.get(Opcode))
+                         .addDef(Reg)
+                         .add(Index)
+                         .addImm(0)
+                         .add(predOps(ARMCC::AL))
+                         .addMemOperand(&MemOp);
+        if (!constrainSelectedInstRegOperands(*Instr, TII, TRI, RBI))
+          return false;
+        I.eraseFromParent();
+        return true;
+      }
+    }
+
     const auto NewOpc = selectLoadStoreOpCode(I.getOpcode(), RegBank, ValSize);
     if (NewOpc == G_LOAD || NewOpc == G_STORE)
       return false;

llvm/lib/Target/ARM/ARMLegalizerInfo.cpp

@@ -29,7 +29,7 @@ static bool AEABI(const ARMSubtarget &ST) {
   return ST.isTargetAEABI() || ST.isTargetGNUAEABI() || ST.isTargetMuslAEABI();
 }
 
-ARMLegalizerInfo::ARMLegalizerInfo(const ARMSubtarget &ST) {
+ARMLegalizerInfo::ARMLegalizerInfo(const ARMSubtarget &ST) : ST(ST) {
   using namespace TargetOpcode;
 
   const LLT p0 = LLT::pointer(0, 32);
@@ -99,9 +99,11 @@ ARMLegalizerInfo::ARMLegalizerInfo(const ARMSubtarget &ST) {
       .minScalar(0, s32);
 
   getActionDefinitionsBuilder(G_CONSTANT)
-      .legalFor({s32, p0})
+      .customFor({s32, p0})
       .clampScalar(0, s32, s32);
 
+  getActionDefinitionsBuilder(G_CONSTANT_POOL).legalFor({p0});
+
   getActionDefinitionsBuilder(G_ICMP)
       .legalForCartesianProduct({s1}, {s32, p0})
       .minScalar(1, s32);
@@ -435,6 +437,13 @@ bool ARMLegalizerInfo::legalizeCustom(LegalizerHelper &Helper, MachineInstr &MI,
     }
     break;
   }
+  case G_CONSTANT: {
+    const ConstantInt *ConstVal = MI.getOperand(1).getCImm();
+    uint64_t ImmVal = ConstVal->getZExtValue();
+    if (ConstantMaterializationCost(ImmVal, &ST) > 2 && !ST.genExecuteOnly())
+      return Helper.lowerConstant(MI) == LegalizerHelper::Legalized;
+    return true;
+  }
   case G_FCONSTANT: {
     // Convert to integer constants, while preserving the binary representation.
     auto AsInteger =

llvm/lib/Target/ARM/ARMLegalizerInfo.h

@@ -59,6 +59,8 @@ class ARMLegalizerInfo : public LegalizerInfo {
   // Get the libcall(s) corresponding to \p Predicate for operands of \p Size
   // bits.
   FCmpLibcallsList getFCmpLibcalls(CmpInst::Predicate, unsigned Size) const;
+
+  const ARMSubtarget &ST;
 };
 } // End llvm namespace.
 #endif

llvm/lib/Target/ARM/ARMRegisterBankInfo.cpp

@@ -329,6 +329,7 @@ ARMRegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
   case G_CONSTANT:
   case G_FRAME_INDEX:
   case G_GLOBAL_VALUE:
+  case G_CONSTANT_POOL:
     OperandsMapping =
         getOperandsMapping({&ARM::ValueMappings[ARM::GPR3OpsIdx], nullptr});
     break;

llvm/test/CodeGen/ARM/GlobalISel/arm-legalize-const.mir

@@ -0,0 +1,20 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple arm-- -run-pass=legalizer %s -o - | FileCheck %s
+
+---
+name:            get_const
+legalized:       false
+regBankSelected: false
+selected:        false
+tracksRegLiveness: true
+body:             |
+  bb.1.entry:
+    ; CHECK-LABEL: name: get_const
+    ; CHECK: [[CONSTANT_POOL:%[0-9]+]]:_(p0) = G_CONSTANT_POOL %const.0
+    ; CHECK-NEXT: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[CONSTANT_POOL]](p0) :: (load (s32) from constant-pool)
+    ; CHECK-NEXT: $r0 = COPY [[LOAD]](s32)
+    ; CHECK-NEXT: MOVPCLR 14 /* CC::al */, $noreg, implicit $r0
+    %0:_(s32) = G_CONSTANT i32 287454020
+    $r0 = COPY %0(s32)
+    MOVPCLR 14 /* CC::al */, $noreg, implicit $r0
+...

llvm/test/CodeGen/ARM/GlobalISel/arm-legalize-fp.mir

@@ -1,9 +1,9 @@
 # RUN: llc -O0 -mtriple arm-linux-gnueabihf -mattr=+vfp2 -float-abi=hard -run-pass=legalizer %s -o - | FileCheck %s -check-prefix CHECK -check-prefix HARD
-# RUN: llc -O0 -mtriple arm-linux-gnueabi -mattr=+vfp2,+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s -check-prefix CHECK -check-prefix SOFT -check-prefix SOFT-AEABI
-# RUN: llc -O0 -mtriple arm-linux-gnu -mattr=+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s  -check-prefix CHECK -check-prefix SOFT -check-prefix SOFT-DEFAULT
+# RUN: llc -O0 -mtriple arm-linux-gnueabi -mattr=+vfp2,+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s -check-prefix CHECK -check-prefix SOFT -check-prefix SOFT-AEABI -check-prefix SOFT_POOL
+# RUN: llc -O0 -mtriple arm-linux-gnu -mattr=+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s  -check-prefix CHECK -check-prefix SOFT -check-prefix SOFT-DEFAULT -check-prefix SOFT_POOL
 # RUN: llc -O0 -mtriple thumb-linux-gnueabihf -mattr=+v6t2,+vfp2 -float-abi=hard -run-pass=legalizer %s -o - | FileCheck %s -check-prefix CHECK -check-prefix HARD
-# RUN: llc -O0 -mtriple thumb-linux-gnueabi -mattr=+v6t2,+vfp2,+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s -check-prefix CHECK -check-prefix SOFT -check-prefix SOFT-AEABI
-# RUN: llc -O0 -mtriple thumb-linux-gnu -mattr=+v6t2,+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s  -check-prefix CHECK -check-prefix SOFT -check-prefix SOFT-DEFAULT
+# RUN: llc -O0 -mtriple thumb-linux-gnueabi -mattr=+v6t2,+vfp2,+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s -check-prefix CHECK -check-prefix SOFT -check-prefix=SOFT-AEABI -check-prefix SOFT_CONST
+# RUN: llc -O0 -mtriple thumb-linux-gnu -mattr=+v6t2,+soft-float -float-abi=soft -run-pass=legalizer %s -o - | FileCheck %s  -check-prefix CHECK -check-prefix SOFT -check-prefix SOFT-DEFAULT -check-prefix SOFT_CONST
 --- |
   define void @test_frem_float() { ret void }
   define void @test_frem_double() { ret void }
@@ -657,10 +657,20 @@ body:             |
   bb.0:
     liveins:
 
+    ; SOFT_POOL: constants:
+    ; SOFT_POOL: id: 0
+    ; SOFT_POOL: value: i32 -1073532109
+    ; SOFT_POOL: id: 1
+    ; SOFT_POOL: value: i32 858993459
+
     ; HARD: [[R:%[0-9]+]]:_(s64) = G_FCONSTANT double -2.4
     ; SOFT-NOT: G_FCONSTANT
-    ; SOFT-DAG: [[HI:%[0-9]+]]:_(s32) = G_CONSTANT i32 -1073532109
-    ; SOFT-DAG: [[LO:%[0-9]+]]:_(s32) = G_CONSTANT i32 858993459
+    ; SOFT_CONST-DAG: [[HI:%[0-9]+]]:_(s32) = G_CONSTANT i32 -1073532109
+    ; SOFT_CONST-DAG: [[LO:%[0-9]+]]:_(s32) = G_CONSTANT i32 858993459
+    ; SOFT_POOL-DAG: [[HIPTR:%[0-9]+]]:_(p0) = G_CONSTANT_POOL %const.0
+    ; SOFT_POOL-DAG: [[HI:%[0-9]+]]:_(s32) = G_LOAD [[HIPTR]]
+    ; SOFT_POOL-DAG: [[LOPTR:%[0-9]+]]:_(p0) = G_CONSTANT_POOL %const.1
+    ; SOFT_POOL-DAG: [[LO:%[0-9]+]]:_(s32) = G_LOAD [[LOPTR]]
     ; SOFT-NOT: G_FCONSTANT
     %0(s64) = G_FCONSTANT double -2.4
     ; HARD-DAG: G_UNMERGE_VALUES [[R]](s64)

llvm/test/CodeGen/ARM/GlobalISel/select-constpool.mir

@@ -0,0 +1,25 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 5
+# RUN: llc -mtriple arm-- -run-pass=instruction-select -verify-machineinstrs %s -o - | FileCheck %s
+
+---
+name:            get_const
+legalized:       true
+regBankSelected: true
+selected:        false
+tracksRegLiveness: true
+constants:
+  - id:              0
+    value:           i32 287454020
+    alignment:       4
+    isTargetSpecific: false
+body:             |
+  bb.1.entry:
+    ; CHECK-LABEL: name: get_const
+    ; CHECK: [[LDRcp:%[0-9]+]]:gpr = LDRcp %const.0, 0, 14 /* CC::al */, $noreg :: (load (s32) from constant-pool)
+    ; CHECK-NEXT: $r0 = COPY [[LDRcp]]
+    ; CHECK-NEXT: MOVPCLR 14 /* CC::al */, $noreg, implicit $r0
+    %1:gprb(p0) = G_CONSTANT_POOL %const.0
+    %0:gprb(s32) = G_LOAD %1(p0) :: (load (s32) from constant-pool)
+    $r0 = COPY %0(s32)
+    MOVPCLR 14 /* CC::al */, $noreg, implicit $r0
+...