[GlobalISel] Avoid translating synthetic constants to new G_CONSTANTS.

Currently, we create a G_CONSTANT for every "synthetic" integer
constant operand (for instance, for the G_GEP offset).
Instead, share the G_CONSTANTs we might have created by going through
the ValueToVReg machinery.

When we're emitting synthetic constants, we do need to get Constants from
the context.  One could argue that we shouldn't modify the context at
all (for instance, this means that we're going to use a tad more memory
if the constant wasn't used elsewhere), but constants are mostly
harmless.  We currently do this for extractvalue and all.

For constant fcmp, this does mean we'll emit an extra COPY, which is not
necessarily more optimal than an extra materialized constant.
But that preserves the current intended design of uniqued G_CONSTANTs,
and the rematerialization problem exists elsewhere and should be
resolved with a single coherent solution.

llvm-svn: 297875

1 files changed, 20 insertions, 17 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 353c4a22fe6..7b09fd815ab 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -190,9 +190,11 @@ bool IRTranslator::translateCompare(const User &U,
   if (CmpInst::isIntPredicate(Pred))
     MIRBuilder.buildICmp(Pred, Res, Op0, Op1);
   else if (Pred == CmpInst::FCMP_FALSE)
-    MIRBuilder.buildConstant(Res, 0);
-  else if  (Pred == CmpInst::FCMP_TRUE)
-    MIRBuilder.buildConstant(Res, 1);
+    MIRBuilder.buildCopy(
+        Res, getOrCreateVReg(*Constant::getNullValue(CI->getType())));
+  else if (Pred == CmpInst::FCMP_TRUE)
+    MIRBuilder.buildCopy(
+        Res, getOrCreateVReg(*Constant::getAllOnesValue(CI->getType())));
   else
     MIRBuilder.buildFCmp(Pred, Res, Op0, Op1);
 
@@ -426,9 +428,10 @@ bool IRTranslator::translateGetElementPtr(const User &U,
 
   Value &Op0 = *U.getOperand(0);
   unsigned BaseReg = getOrCreateVReg(Op0);
-  LLT PtrTy = getLLTForType(*Op0.getType(), *DL);
-  unsigned PtrSize = DL->getPointerSizeInBits(PtrTy.getAddressSpace());
-  LLT OffsetTy = LLT::scalar(PtrSize);
+  Type *PtrIRTy = Op0.getType();
+  LLT PtrTy = getLLTForType(*PtrIRTy, *DL);
+  Type *OffsetIRTy = DL->getIntPtrType(PtrIRTy);
+  LLT OffsetTy = getLLTForType(*OffsetIRTy, *DL);
 
   int64_t Offset = 0;
   for (gep_type_iterator GTI = gep_type_begin(&U), E = gep_type_end(&U);
@@ -450,8 +453,8 @@ bool IRTranslator::translateGetElementPtr(const User &U,
 
       if (Offset != 0) {
         unsigned NewBaseReg = MRI->createGenericVirtualRegister(PtrTy);
-        unsigned OffsetReg = MRI->createGenericVirtualRegister(OffsetTy);
-        MIRBuilder.buildConstant(OffsetReg, Offset);
+        unsigned OffsetReg =
+            getOrCreateVReg(*ConstantInt::get(OffsetIRTy, Offset));
         MIRBuilder.buildGEP(NewBaseReg, BaseReg, OffsetReg);
 
         BaseReg = NewBaseReg;
@@ -459,8 +462,8 @@ bool IRTranslator::translateGetElementPtr(const User &U,
       }
 
       // N = N + Idx * ElementSize;
-      unsigned ElementSizeReg = MRI->createGenericVirtualRegister(OffsetTy);
-      MIRBuilder.buildConstant(ElementSizeReg, ElementSize);
+      unsigned ElementSizeReg =
+          getOrCreateVReg(*ConstantInt::get(OffsetIRTy, ElementSize));
 
       unsigned IdxReg = getOrCreateVReg(*Idx);
       if (MRI->getType(IdxReg) != OffsetTy) {
@@ -479,8 +482,7 @@ bool IRTranslator::translateGetElementPtr(const User &U,
   }
 
   if (Offset != 0) {
-    unsigned OffsetReg = MRI->createGenericVirtualRegister(OffsetTy);
-    MIRBuilder.buildConstant(OffsetReg, Offset);
+    unsigned OffsetReg = getOrCreateVReg(*ConstantInt::get(OffsetIRTy, Offset));
     MIRBuilder.buildGEP(getOrCreateVReg(U), BaseReg, OffsetReg);
     return true;
   }
@@ -561,8 +563,8 @@ bool IRTranslator::translateOverflowIntrinsic(const CallInst &CI, unsigned Op,
                  .addUse(getOrCreateVReg(*CI.getOperand(1)));
 
   if (Op == TargetOpcode::G_UADDE || Op == TargetOpcode::G_USUBE) {
-    unsigned Zero = MRI->createGenericVirtualRegister(s1);
-    EntryBuilder.buildConstant(Zero, 0);
+    unsigned Zero = getOrCreateVReg(
+        *Constant::getNullValue(Type::getInt1Ty(CI.getContext())));
     MIB.addUse(Zero);
   }
 
@@ -914,7 +916,8 @@ bool IRTranslator::translateAlloca(const User &U,
 
   unsigned NumElts = getOrCreateVReg(*AI.getArraySize());
 
-  LLT IntPtrTy = LLT::scalar(DL->getPointerSizeInBits());
+  Type *IntPtrIRTy = DL->getIntPtrType(AI.getType());
+  LLT IntPtrTy = getLLTForType(*IntPtrIRTy, *DL);
   if (MRI->getType(NumElts) != IntPtrTy) {
     unsigned ExtElts = MRI->createGenericVirtualRegister(IntPtrTy);
     MIRBuilder.buildZExtOrTrunc(ExtElts, NumElts);
@@ -922,8 +925,8 @@ bool IRTranslator::translateAlloca(const User &U,
   }
 
   unsigned AllocSize = MRI->createGenericVirtualRegister(IntPtrTy);
-  unsigned TySize = MRI->createGenericVirtualRegister(IntPtrTy);
-  MIRBuilder.buildConstant(TySize, -DL->getTypeAllocSize(Ty));
+  unsigned TySize =
+      getOrCreateVReg(*ConstantInt::get(IntPtrIRTy, -DL->getTypeAllocSize(Ty)));
   MIRBuilder.buildMul(AllocSize, NumElts, TySize);
 
   LLT PtrTy = getLLTForType(*AI.getType(), *DL);