From 8eaa1ef0d88c36dbf90e191c8852ea46bf4841c9 Mon Sep 17 00:00:00 2001 From: Chenbing Zheng <Chenbing.Zheng@streamcomputing.com> Date: Sat, 7 May 2022 15:34:57 +0800 Subject: [PATCH] [InstCombine] add casts from splat-a-bit pattern if necessary Splatting a bit of constant-index across a value: sext (ashr (trunc iN X to iM), M-1) to iN --> ashr (shl X, N-M), N-1 If the dest type is different, use a cast (adjust use check). https://alive2.llvm.org/ce/z/acAan3 Reviewed By: spatel Differential Revision: https://reviews.llvm.org/D124590 --- .../InstCombine/InstCombineCasts.cpp | 20 ++++++++++++------- llvm/test/Transforms/InstCombine/sext.ll | 14 ++++++------- 2 files changed, 19 insertions(+), 15 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index 9a89aa557258..4fbbdd5d6dbc 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -1592,14 +1592,20 @@ Instruction *InstCombinerImpl::visitSExt(SExtInst &CI) { // Splatting a bit of constant-index across a value: // sext (ashr (trunc iN X to iM), M-1) to iN --> ashr (shl X, N-M), N-1 - // TODO: If the dest type is different, use a cast (adjust use check). + // If the dest type is different, use a cast (adjust use check). if (match(Src, m_OneUse(m_AShr(m_Trunc(m_Value(X)), - m_SpecificInt(SrcBitSize - 1)))) && - X->getType() == DestTy) { - Constant *ShlAmtC = ConstantInt::get(DestTy, DestBitSize - SrcBitSize); - Constant *AshrAmtC = ConstantInt::get(DestTy, DestBitSize - 1); - Value *Shl = Builder.CreateShl(X, ShlAmtC); - return BinaryOperator::CreateAShr(Shl, AshrAmtC); + m_SpecificInt(SrcBitSize - 1))))) { + Type *XTy = X->getType(); + unsigned XBitSize = XTy->getScalarSizeInBits(); + Constant *ShlAmtC = ConstantInt::get(XTy, XBitSize - SrcBitSize); + Constant *AshrAmtC = ConstantInt::get(XTy, XBitSize - 1); + if (XTy == DestTy) + return BinaryOperator::CreateAShr(Builder.CreateShl(X, ShlAmtC), + AshrAmtC); + if (cast<BinaryOperator>(Src)->getOperand(0)->hasOneUse()) { + Value *Ashr = Builder.CreateAShr(Builder.CreateShl(X, ShlAmtC), AshrAmtC); + return CastInst::CreateIntegerCast(Ashr, DestTy, /* isSigned */ true); + } } if (match(Src, m_VScale(DL))) { diff --git a/llvm/test/Transforms/InstCombine/sext.ll b/llvm/test/Transforms/InstCombine/sext.ll index 2e5735f1c133..e6d220d8f9b7 100644 --- a/llvm/test/Transforms/InstCombine/sext.ll +++ b/llvm/test/Transforms/InstCombine/sext.ll @@ -381,13 +381,11 @@ define i32 @smear_set_bit_wrong_shift_amount(i32 %x) { ret i32 %s } -; TODO: this could be mask+compare+sext or shifts+trunc - define i16 @smear_set_bit_different_dest_type(i32 %x) { ; CHECK-LABEL: @smear_set_bit_different_dest_type( -; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i8 -; CHECK-NEXT: [[A:%.*]] = ashr i8 [[T]], 7 -; CHECK-NEXT: [[S:%.*]] = sext i8 [[A]] to i16 +; CHECK-NEXT: [[TMP1:%.*]] = shl i32 [[X:%.*]], 24 +; CHECK-NEXT: [[TMP2:%.*]] = ashr i32 [[TMP1]], 31 +; CHECK-NEXT: [[S:%.*]] = trunc i32 [[TMP2]] to i16 ; CHECK-NEXT: ret i16 [[S]] ; %t = trunc i32 %x to i8 @@ -415,9 +413,9 @@ define i16 @smear_set_bit_different_dest_type_extra_use(i32 %x) { define i64 @smear_set_bit_different_dest_type_wider_dst(i32 %x) { ; CHECK-LABEL: @smear_set_bit_different_dest_type_wider_dst( -; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i8 -; CHECK-NEXT: [[A:%.*]] = ashr i8 [[T]], 7 -; CHECK-NEXT: [[S:%.*]] = sext i8 [[A]] to i64 +; CHECK-NEXT: [[TMP1:%.*]] = shl i32 [[X:%.*]], 24 +; CHECK-NEXT: [[TMP2:%.*]] = ashr i32 [[TMP1]], 31 +; CHECK-NEXT: [[S:%.*]] = sext i32 [[TMP2]] to i64 ; CHECK-NEXT: ret i64 [[S]] ; %t = trunc i32 %x to i8