[PATCH] D125951: [InstCombine] bitcast (extractelement <1 x elt>, dest) -> bitcast(<1 x elt>, dest)

[Chenbing.Zheng via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Chenbing.Zheng marked an inline comment as done.
Closed by commit rGef256ed58ebf: [InstCombine] bitcast (extractelement <1 x elt>, dest) -> bitcast(<1 x elt>… (authored by Chenbing.Zheng).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D125951/new/

https://reviews.llvm.org/D125951

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
  llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll
  llvm/test/Transforms/InstCombine/bitcast.ll


Index: llvm/test/Transforms/InstCombine/bitcast.ll
===================================================================
--- llvm/test/Transforms/InstCombine/bitcast.ll
+++ llvm/test/Transforms/InstCombine/bitcast.ll
@@ -402,14 +402,9 @@
   ret i64 %bc2
 }
 
-; TODO: This should return %A.
-
 define <2 x i32> @bitcast_extelt3(<2 x i32> %A) {
 ; CHECK-LABEL: @bitcast_extelt3(
-; CHECK-NEXT:    [[BC1:%.*]] = bitcast <2 x i32> [[A:%.*]] to <1 x i64>
-; CHECK-NEXT:    [[EXT:%.*]] = extractelement <1 x i64> [[BC1]], i64 0
-; CHECK-NEXT:    [[BC2:%.*]] = bitcast i64 [[EXT]] to <2 x i32>
-; CHECK-NEXT:    ret <2 x i32> [[BC2]]
+; CHECK-NEXT:    ret <2 x i32> [[A:%.*]]
 ;
   %bc1 = bitcast <2 x i32> %A to <1 x i64>
   %ext = extractelement <1 x i64> %bc1, i32 0
@@ -433,8 +428,7 @@
 
 define <2 x i32> @bitcast_extelt5(<1 x i64> %A) {
 ; CHECK-LABEL: @bitcast_extelt5(
-; CHECK-NEXT:    [[EXT:%.*]] = extractelement <1 x i64> [[A:%.*]], i64 0
-; CHECK-NEXT:    [[BC:%.*]] = bitcast i64 [[EXT]] to <2 x i32>
+; CHECK-NEXT:    [[BC:%.*]] = bitcast <1 x i64> [[A:%.*]] to <2 x i32>
 ; CHECK-NEXT:    ret <2 x i32> [[BC]]
 ;
   %ext = extractelement <1 x i64> %A, i32 0
Index: llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll
===================================================================
--- llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll
+++ llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll
@@ -353,14 +353,9 @@
   ret i64 %bc2
 }
 
-; TODO: This should return %A.
-
 define <2 x i32> @bitcast_extelt3(<2 x i32> %A) {
 ; CHECK-LABEL: @bitcast_extelt3(
-; CHECK-NEXT:    [[BC1:%.*]] = bitcast <2 x i32> [[A:%.*]] to <1 x i64>
-; CHECK-NEXT:    [[EXT:%.*]] = extractelement <1 x i64> [[BC1]], i64 0
-; CHECK-NEXT:    [[BC2:%.*]] = bitcast i64 [[EXT]] to <2 x i32>
-; CHECK-NEXT:    ret <2 x i32> [[BC2]]
+; CHECK-NEXT:    ret <2 x i32> [[A:%.*]]
 ;
   %bc1 = bitcast <2 x i32> %A to <1 x i64>
   %ext = extractelement <1 x i64> %bc1, i32 0
Index: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2363,13 +2363,20 @@
   // The bitcast must be to a vectorizable type, otherwise we can't make a new
   // type to extract from.
   Type *DestType = BitCast.getType();
-  if (!VectorType::isValidElementType(DestType))
-    return nullptr;
+  VectorType *VecType = cast<VectorType>(VecOp->getType());
+  if (VectorType::isValidElementType(DestType)) {
+    auto *NewVecType = VectorType::get(DestType, VecType);
+    auto *NewBC = IC.Builder.CreateBitCast(VecOp, NewVecType, "bc");
+    return ExtractElementInst::Create(NewBC, Index);
+  }
 
-  auto *NewVecType =
-      VectorType::get(DestType, cast<VectorType>(VecOp->getType()));
-  auto *NewBC = IC.Builder.CreateBitCast(VecOp, NewVecType, "bc");
-  return ExtractElementInst::Create(NewBC, Index);
+  // Only solve DestType is vector to avoid inverse transform in visitBitCast.
+  // bitcast (extractelement <1 x elt>, dest) -> bitcast(<1 x elt>, dest)
+  auto *FixedVType = dyn_cast<FixedVectorType>(VecType);
+  if (DestType->isVectorTy() && FixedVType && FixedVType->getNumElements() == 1)
+    return CastInst::Create(Instruction::BitCast, VecOp, DestType);
+
+  return nullptr;
 }
 
 /// Change the type of a bitwise logic operation if we can eliminate a bitcast.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D125951.432817.patch
Type: text/x-patch
Size: 3437 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220530/ac551c42/attachment.bin>