[PATCH] Canonicalize addrspacecast between different pointer types.

[Matt Arsenault]

Cast the address space with the same pointer element type
and then bitcast the type in the new address space.
    
addrspacecast X addrspace(M)* to Y addrspace(N)*
->
bitcast X addrspace(N)* (addrspacecast X addrspace(M)* to X addrspace(N)*) to Y addrspace(N)*



http://llvm-reviews.chandlerc.com/D2186

Files:
  lib/IR/Instructions.cpp
  lib/Transforms/InstCombine/InstCombineCasts.cpp
  test/Transforms/InstCombine/addrspacecast.ll

Index: lib/IR/Instructions.cpp
===================================================================
--- lib/IR/Instructions.cpp
+++ lib/IR/Instructions.cpp
@@ -2282,38 +2282,25 @@
       return 0;
     }
     case 12: {
-      // addrspacecast, addrspacecast -> bitcast,       if SrcAS == DstAS
       // addrspacecast, addrspacecast -> addrspacecast, if SrcAS != DstAS
       if (SrcTy->getPointerAddressSpace() != DstTy->getPointerAddressSpace())
         return Instruction::AddrSpaceCast;
-      return Instruction::BitCast;
+      return 0;
     }
     case 13:
-      // FIXME: this state can be merged with (1), but the following assert
-      // is useful to check the correcteness of the sequence due to semantic
-      // change of bitcast.
-      assert(
-        SrcTy->isPtrOrPtrVectorTy() &&
-        MidTy->isPtrOrPtrVectorTy() &&
-        DstTy->isPtrOrPtrVectorTy() &&
-        SrcTy->getPointerAddressSpace() != MidTy->getPointerAddressSpace() &&
-        MidTy->getPointerAddressSpace() == DstTy->getPointerAddressSpace() &&
-        "Illegal addrspacecast, bitcast sequence!");
-      // Allowed, use first cast's opcode
-      return firstOp;
+      // addrspacecast, bitcast -> addrspacecast if the pointer element types
+      // are the same.
+      if (SrcTy->getPointerElementType() == DstTy->getPointerElementType())
+        return Instruction::AddrSpaceCast;
+      return 0;
+
     case 14:
-      // FIXME: this state can be merged with (2), but the following assert
-      // is useful to check the correcteness of the sequence due to semantic
-      // change of bitcast.
-      assert(
-        SrcTy->isPtrOrPtrVectorTy() &&
-        MidTy->isPtrOrPtrVectorTy() &&
-        DstTy->isPtrOrPtrVectorTy() &&
-        SrcTy->getPointerAddressSpace() == MidTy->getPointerAddressSpace() &&
-        MidTy->getPointerAddressSpace() != DstTy->getPointerAddressSpace() &&
-        "Illegal bitcast, addrspacecast sequence!");
-      // Allowed, use second cast's opcode
-      return secondOp;
+      // bitcast, addrspacecast -> addrspacecast if the pointer element types
+      // are the same.
+      if (MidTy->getPointerElementType() == DstTy->getPointerElementType())
+        return Instruction::AddrSpaceCast;
+      return 0;
+
     case 15:
       // FIXME: this state can be merged with (1), but the following assert
       // is useful to check the correcteness of the sequence due to semantic
Index: lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1853,5 +1853,22 @@
 }
 
 Instruction *InstCombiner::visitAddrSpaceCast(AddrSpaceCastInst &CI) {
-  return commonCastTransforms(CI);
+  // If the destination pointer element type is not the the same as the source's
+  // do the addrspacecast to the same type, and then the bitcast in the new
+  // address space. This allows the cast to be exposed to other transforms.
+  Value *Src = CI.getOperand(0);
+  PointerType *SrcTy = cast<PointerType>(Src->getType()->getScalarType());
+  PointerType *DestTy = cast<PointerType>(CI.getType()->getScalarType());
+
+  Type *SrcElemTy = SrcTy->getElementType();
+  if (SrcElemTy != DestTy->getElementType()) {
+    Type *MidTy = PointerType::get(SrcElemTy, DestTy->getAddressSpace());
+    if (CI.getType()->isVectorTy()) // Handle vectors of pointers.
+      MidTy = VectorType::get(MidTy, CI.getType()->getVectorNumElements());
+
+    Value *NewASCast = Builder->CreateAddrSpaceCast(Src, MidTy);
+    return new BitCastInst(NewASCast, CI.getType());
+  }
+
+  return commonPointerCastTransforms(CI);
 }
Index: test/Transforms/InstCombine/addrspacecast.ll
===================================================================
--- test/Transforms/InstCombine/addrspacecast.ll
+++ test/Transforms/InstCombine/addrspacecast.ll
@@ -22,10 +22,77 @@
 
 define float* @combine_redundant_addrspacecast_types(i32 addrspace(1)* %x) nounwind {
 ; CHECK-LABEL: @combine_redundant_addrspacecast_types(
-; CHECK: addrspacecast i32 addrspace(1)* %x to float*
+; CHECK-NEXT: addrspacecast i32 addrspace(1)* %x to i32*
+; CHECK-NEXT: bitcast i32* %1 to float*
 ; CHECK-NEXT: ret
   %y = addrspacecast i32 addrspace(1)* %x to i32 addrspace(3)*
   %z = addrspacecast i32 addrspace(3)* %y to float*
   ret float* %z
 }
 
+define <4 x float*> @combine_redundant_addrspacecast_types_vector(<4 x i32 addrspace(1)*> %x) nounwind {
+; CHECK-LABEL: @combine_redundant_addrspacecast_types_vector(
+; CHECK-NEXT: addrspacecast <4 x i32 addrspace(1)*> %x to <4 x i32*>
+; CHECK-NEXT: bitcast <4 x i32*> %1 to <4 x float*>
+; CHECK-NEXT: ret
+  %y = addrspacecast <4 x i32 addrspace(1)*> %x to <4 x i32 addrspace(3)*>
+  %z = addrspacecast <4 x i32 addrspace(3)*> %y to <4 x float*>
+  ret <4 x float*> %z
+}
+
+define float addrspace(2)* @combine_addrspacecast_bitcast_1(i32 addrspace(1)* %x) nounwind {
+; CHECK-LABEL: @combine_addrspacecast_bitcast_1(
+; CHECK-NEXT: addrspacecast i32 addrspace(1)* %x to i32 addrspace(2)*
+; CHECK-NEXT: bitcast i32 addrspace(2)* %y to float addrspace(2)*
+; CHECK-NEXT: ret
+  %y = addrspacecast i32 addrspace(1)* %x to i32 addrspace(2)*
+  %z = bitcast i32 addrspace(2)* %y to float addrspace(2)*
+  ret float addrspace(2)* %z
+}
+
+define i32 addrspace(2)* @combine_addrspacecast_bitcast_2(i32 addrspace(1)* %x) nounwind {
+; CHECK-LABEL: @combine_addrspacecast_bitcast_2(
+; CHECK: addrspacecast i32 addrspace(1)* %x to i32 addrspace(2)*
+; CHECK-NEXT: ret
+  %y = addrspacecast i32 addrspace(1)* %x to float addrspace(2)*
+  %z = bitcast float addrspace(2)* %y to i32 addrspace(2)*
+  ret i32 addrspace(2)* %z
+}
+
+define i32 addrspace(2)* @combine_bitcast_addrspacecast_1(i32 addrspace(1)* %x) nounwind {
+; CHECK-LABEL: @combine_bitcast_addrspacecast_1(
+; CHECK: addrspacecast i32 addrspace(1)* %x to i32 addrspace(2)*
+; CHECK-NEXT: ret
+  %y = bitcast i32 addrspace(1)* %x to i8 addrspace(1)*
+  %z = addrspacecast i8 addrspace(1)* %y to i32 addrspace(2)*
+  ret i32 addrspace(2)* %z
+}
+
+define float addrspace(2)* @combine_bitcast_addrspacecast_2(i32 addrspace(1)* %x) nounwind {
+; CHECK-LABEL: @combine_bitcast_addrspacecast_2(
+; CHECK: addrspacecast i32 addrspace(1)* %x to i32 addrspace(2)*
+; CHECK: bitcast i32 addrspace(2)* %1 to float addrspace(2)*
+; CHECK-NEXT: ret
+  %y = bitcast i32 addrspace(1)* %x to i8 addrspace(1)*
+  %z = addrspacecast i8 addrspace(1)* %y to float addrspace(2)*
+  ret float addrspace(2)* %z
+}
+
+define float addrspace(2)* @combine_addrspacecast_types(i32 addrspace(1)* %x) nounwind {
+; CHECK-LABEL: @combine_addrspacecast_types(
+; CHECK-NEXT: addrspacecast i32 addrspace(1)* %x to i32 addrspace(2)*
+; CHECK-NEXT: bitcast i32 addrspace(2)* %1 to float addrspace(2)*
+; CHECK-NEXT: ret
+  %y = addrspacecast i32 addrspace(1)* %x to float addrspace(2)*
+  ret float addrspace(2)* %y
+}
+
+define <4 x float addrspace(2)*> @combine_addrspacecast_types_vector(<4 x i32 addrspace(1)*> %x) nounwind {
+; CHECK-LABEL: @combine_addrspacecast_types_vector(
+; CHECK-NEXT: addrspacecast <4 x i32 addrspace(1)*> %x to <4 x i32 addrspace(2)*>
+; CHECK-NEXT: bitcast <4 x i32 addrspace(2)*> %1 to <4 x float addrspace(2)*>
+; CHECK-NEXT: ret
+  %y = addrspacecast <4 x i32 addrspace(1)*> %x to <4 x float addrspace(2)*>
+  ret <4 x float addrspace(2)*> %y
+}
+
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