[llvm] [VectorCombine] Relax vector type constraint on bitop(bitcast, constant) (PR #157246)
Hongyu Chen via llvm-commits
llvm-commits at lists.llvm.org
Sun Sep 7 06:30:47 PDT 2025
https://github.com/XChy updated https://github.com/llvm/llvm-project/pull/157246
>From 280d9f7d12cc44c267c9ba77ec24d65d8bd82d28 Mon Sep 17 00:00:00 2001
From: XChy <xxs_chy at outlook.com>
Date: Sat, 6 Sep 2025 17:06:46 +0800
Subject: [PATCH 1/4] Precommit tests
---
.../VectorCombine/X86/bitop-of-castops.ll | 60 +++++++++++++++++++
1 file changed, 60 insertions(+)
diff --git a/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll b/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll
index ca707ca08f169..fe62f91480cd2 100644
--- a/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll
+++ b/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll
@@ -420,3 +420,63 @@ define <4 x i32> @or_zext_nneg_multiconstant(<4 x i8> %a) {
%or = or <4 x i32> %z1, <i32 240, i32 1, i32 242, i32 3>
ret <4 x i32> %or
}
+
+; Negative test: bitcast from scalar float to vector int (optimization should not apply)
+define <2 x i16> @and_bitcast_f32_to_v2i16_constant(float %a) {
+; CHECK-LABEL: @and_bitcast_f32_to_v2i16_constant(
+; CHECK-NEXT: [[BC2:%.*]] = bitcast float [[B:%.*]] to <2 x i16>
+; CHECK-NEXT: [[AND:%.*]] = and <2 x i16> <i16 0, i16 1>, [[BC2]]
+; CHECK-NEXT: ret <2 x i16> [[AND]]
+;
+ %bc = bitcast float %a to <2 x i16>
+ %and = and <2 x i16> <i16 0, i16 1>, %bc
+ ret <2 x i16> %and
+}
+
+; Negative test: bitcast from vector float to scalar int (optimization should not apply)
+define i64 @and_bitcast_v2f32_to_i64_constant(<2 x float> %a) {
+; CHECK-LABEL: @and_bitcast_v2f32_to_i64_constant(
+; CHECK-NEXT: [[BC2:%.*]] = bitcast <2 x float> [[B:%.*]] to i64
+; CHECK-NEXT: [[AND:%.*]] = and i64 123, [[BC2]]
+; CHECK-NEXT: ret i64 [[AND]]
+;
+ %bc = bitcast <2 x float> %a to i64
+ %and = and i64 123, %bc
+ ret i64 %and
+}
+
+; Test no-op bitcast
+define i16 @xor_bitcast_i16_to_i16_constant(i16 %a) {
+; CHECK-LABEL: @xor_bitcast_i16_to_i16_constant(
+; CHECK-NEXT: [[BC2:%.*]] = bitcast i16 [[B:%.*]] to i16
+; CHECK-NEXT: [[OR:%.*]] = xor i16 123, [[BC2]]
+; CHECK-NEXT: ret i16 [[OR]]
+;
+ %bc = bitcast i16 %a to i16
+ %or = xor i16 123, %bc
+ ret i16 %or
+}
+
+; Test bitwise operations with integer vector to integer bitcast
+define <16 x i1> @xor_bitcast_i16_to_v16i1_constant(i16 %a) {
+; CHECK-LABEL: @xor_bitcast_i16_to_v16i1_constant(
+; CHECK-NEXT: [[BC2:%.*]] = bitcast i16 [[B:%.*]] to <16 x i1>
+; CHECK-NEXT: [[OR:%.*]] = xor <16 x i1> [[BC2]], splat (i1 true)
+; CHECK-NEXT: ret <16 x i1> [[OR]]
+;
+ %bc = bitcast i16 %a to <16 x i1>
+ %or = xor <16 x i1> %bc, splat (i1 true)
+ ret <16 x i1> %or
+}
+
+; Test bitwise operations with integer vector to integer bitcast
+define i16 @or_bitcast_v16i1_to_i16_constant(<16 x i1> %a) {
+; CHECK-LABEL: @or_bitcast_v16i1_to_i16_constant(
+; CHECK-NEXT: [[BC2:%.*]] = bitcast <16 x i1> [[B:%.*]] to i16
+; CHECK-NEXT: [[OR:%.*]] = or i16 [[BC2]], 3
+; CHECK-NEXT: ret i16 [[OR]]
+;
+ %bc = bitcast <16 x i1> %a to i16
+ %or = or i16 %bc, 3
+ ret i16 %or
+}
>From 3caa1e152b591ecddabe433f66abc1d8b43110b0 Mon Sep 17 00:00:00 2001
From: XChy <xxs_chy at outlook.com>
Date: Sat, 6 Sep 2025 17:14:56 +0800
Subject: [PATCH 2/4] [VectorCombine] Relax vector type constraint in
foldBitOpOfCastConstant
---
.../Transforms/Vectorize/VectorCombine.cpp | 27 +++++++++----------
.../VectorCombine/X86/bitop-of-castops.ll | 6 ++---
2 files changed, 16 insertions(+), 17 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 6e46547b15b2b..cea818350103a 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -1013,19 +1013,20 @@ bool VectorCombine::foldBitOpOfCastConstant(Instruction &I) {
Value *LHSSrc = LHSCast->getOperand(0);
- // Only handle vector types with integer elements
- auto *SrcVecTy = dyn_cast<FixedVectorType>(LHSSrc->getType());
- auto *DstVecTy = dyn_cast<FixedVectorType>(I.getType());
- if (!SrcVecTy || !DstVecTy)
+ // Only handle vector types with integer elements if the cast is not bitcast
+ auto *SrcTy = LHSSrc->getType();
+ auto *DstTy = I.getType();
+ if (CastOpcode != Instruction::BitCast &&
+ (!isa<FixedVectorType>(SrcTy) || !!isa<FixedVectorType>(DstTy)))
return false;
- if (!SrcVecTy->getScalarType()->isIntegerTy() ||
- !DstVecTy->getScalarType()->isIntegerTy())
+ if (!SrcTy->getScalarType()->isIntegerTy() ||
+ !DstTy->getScalarType()->isIntegerTy())
return false;
// Find the constant InvC, such that castop(InvC) equals to C.
PreservedCastFlags RHSFlags;
- Constant *InvC = getLosslessInvCast(C, SrcVecTy, CastOpcode, *DL, RHSFlags);
+ Constant *InvC = getLosslessInvCast(C, SrcTy, CastOpcode, *DL, RHSFlags);
if (!InvC)
return false;
@@ -1034,20 +1035,18 @@ bool VectorCombine::foldBitOpOfCastConstant(Instruction &I) {
// NewCost = bitlogic + cast
// Calculate specific costs for each cast with instruction context
- InstructionCost LHSCastCost =
- TTI.getCastInstrCost(CastOpcode, DstVecTy, SrcVecTy,
- TTI::CastContextHint::None, CostKind, LHSCast);
+ InstructionCost LHSCastCost = TTI.getCastInstrCost(
+ CastOpcode, DstTy, SrcTy, TTI::CastContextHint::None, CostKind, LHSCast);
InstructionCost OldCost =
- TTI.getArithmeticInstrCost(I.getOpcode(), DstVecTy, CostKind) +
- LHSCastCost;
+ TTI.getArithmeticInstrCost(I.getOpcode(), DstTy, CostKind) + LHSCastCost;
// For new cost, we can't provide an instruction (it doesn't exist yet)
InstructionCost GenericCastCost = TTI.getCastInstrCost(
- CastOpcode, DstVecTy, SrcVecTy, TTI::CastContextHint::None, CostKind);
+ CastOpcode, DstTy, SrcTy, TTI::CastContextHint::None, CostKind);
InstructionCost NewCost =
- TTI.getArithmeticInstrCost(I.getOpcode(), SrcVecTy, CostKind) +
+ TTI.getArithmeticInstrCost(I.getOpcode(), SrcTy, CostKind) +
GenericCastCost;
// Account for multi-use casts using specific costs
diff --git a/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll b/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll
index fe62f91480cd2..c6253a7b858ad 100644
--- a/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll
+++ b/llvm/test/Transforms/VectorCombine/X86/bitop-of-castops.ll
@@ -460,9 +460,9 @@ define i16 @xor_bitcast_i16_to_i16_constant(i16 %a) {
; Test bitwise operations with integer vector to integer bitcast
define <16 x i1> @xor_bitcast_i16_to_v16i1_constant(i16 %a) {
; CHECK-LABEL: @xor_bitcast_i16_to_v16i1_constant(
-; CHECK-NEXT: [[BC2:%.*]] = bitcast i16 [[B:%.*]] to <16 x i1>
-; CHECK-NEXT: [[OR:%.*]] = xor <16 x i1> [[BC2]], splat (i1 true)
-; CHECK-NEXT: ret <16 x i1> [[OR]]
+; CHECK-NEXT: [[B:%.*]] = xor i16 [[A:%.*]], -1
+; CHECK-NEXT: [[BC2:%.*]] = bitcast i16 [[B]] to <16 x i1>
+; CHECK-NEXT: ret <16 x i1> [[BC2]]
;
%bc = bitcast i16 %a to <16 x i1>
%or = xor <16 x i1> %bc, splat (i1 true)
>From 67e3093fd603ea88a8d7fb4fb6427b52795429b1 Mon Sep 17 00:00:00 2001
From: XChy <xxs_chy at outlook.com>
Date: Sun, 7 Sep 2025 21:24:16 +0800
Subject: [PATCH 3/4] update comment
---
llvm/lib/Transforms/Vectorize/VectorCombine.cpp | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index cea818350103a..296416c03a9e5 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -1013,17 +1013,20 @@ bool VectorCombine::foldBitOpOfCastConstant(Instruction &I) {
Value *LHSSrc = LHSCast->getOperand(0);
- // Only handle vector types with integer elements if the cast is not bitcast
auto *SrcTy = LHSSrc->getType();
auto *DstTy = I.getType();
+ // Bitcasts can handle scalar/vector mixes, such as i16 -> <16 x i1>.
+ // Other casts only handle vector types with integer elements.
if (CastOpcode != Instruction::BitCast &&
- (!isa<FixedVectorType>(SrcTy) || !!isa<FixedVectorType>(DstTy)))
+ (!isa<FixedVectorType>(SrcTy) || !isa<FixedVectorType>(DstTy)))
return false;
+ // Only integer scalar/vector values are legal for bitwise logic operations.
if (!SrcTy->getScalarType()->isIntegerTy() ||
!DstTy->getScalarType()->isIntegerTy())
return false;
+
// Find the constant InvC, such that castop(InvC) equals to C.
PreservedCastFlags RHSFlags;
Constant *InvC = getLosslessInvCast(C, SrcTy, CastOpcode, *DL, RHSFlags);
>From 11f3332dedcf1693e79e948dbb718660830ec9c3 Mon Sep 17 00:00:00 2001
From: XChy <xxs_chy at outlook.com>
Date: Sun, 7 Sep 2025 21:30:30 +0800
Subject: [PATCH 4/4] format
---
llvm/lib/Transforms/Vectorize/VectorCombine.cpp | 1 -
1 file changed, 1 deletion(-)
diff --git a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
index 296416c03a9e5..b1c7a2682785b 100644
--- a/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
+++ b/llvm/lib/Transforms/Vectorize/VectorCombine.cpp
@@ -1026,7 +1026,6 @@ bool VectorCombine::foldBitOpOfCastConstant(Instruction &I) {
!DstTy->getScalarType()->isIntegerTy())
return false;
-
// Find the constant InvC, such that castop(InvC) equals to C.
PreservedCastFlags RHSFlags;
Constant *InvC = getLosslessInvCast(C, SrcTy, CastOpcode, *DL, RHSFlags);
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