[llvm] ef256ed - [InstCombine] bitcast (extractelement <1 x elt>, dest) -> bitcast(<1 x elt>, dest)

[Chenbing Zheng via llvm-commits]

Author: Chenbing Zheng
Date: 2022-05-30T10:16:32+08:00
New Revision: ef256ed58ebf4689ec8d8fffaee529063f0b8729

URL: https://github.com/llvm/llvm-project/commit/ef256ed58ebf4689ec8d8fffaee529063f0b8729
DIFF: https://github.com/llvm/llvm-project/commit/ef256ed58ebf4689ec8d8fffaee529063f0b8729.diff

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

Only solve dest type is vector to avoid inverse transform in visitBitCast.

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D125951

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 9fb266bd60c75..c3fb0b542e5c7 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2363,13 +2363,20 @@ static Instruction *canonicalizeBitCastExtElt(BitCastInst &BitCast,
   // 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.

diff  --git a/llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll b/llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll
index 95edb21f7340b..c987c2885115d 100644
--- a/llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll
+++ b/llvm/test/Transforms/InstCombine/bitcast-inseltpoison.ll
@@ -353,14 +353,9 @@ define i64 @bitcast_extelt2(<4 x float> %A) {
   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

diff  --git a/llvm/test/Transforms/InstCombine/bitcast.ll b/llvm/test/Transforms/InstCombine/bitcast.ll
index 6819355828079..1346885f69880 100644
--- a/llvm/test/Transforms/InstCombine/bitcast.ll
+++ b/llvm/test/Transforms/InstCombine/bitcast.ll
@@ -402,14 +402,9 @@ define i64 @bitcast_extelt2(<4 x float> %A) {
   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 double @bitcast_extelt4(i128 %A) {
 
 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