From: Daan Sprenkels <daan@dsprenkels.com>
Date: Sun, 29 Mar 2020 19:48:54 +0000 (+0200)
Subject: [InstCombine] Transform extelt-trunc -> bitcast-extelt
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=464b9aeafe29104a1a8391f43f91835eeca473b3;p=platform%2Fupstream%2Fllvm.git

[InstCombine] Transform extelt-trunc -> bitcast-extelt

Canonicalize the case when a scalar extracted from a vector is
truncated.  Transform such cases to bitcast-then-extractelement.
This will enable erasing the truncate operation.

This commit fixes PR45314.

reviewers: spatel

Differential revision: https://reviews.llvm.org/D76983
---

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index afdddad..58f9dce 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -690,6 +690,7 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
 
   Value *Src = CI.getOperand(0);
   Type *DestTy = CI.getType(), *SrcTy = Src->getType();
+  ConstantInt *Cst;
 
   // Attempt to truncate the entire input expression tree to the destination
   // type.   Only do this if the dest type is a simple type, don't convert the
@@ -758,7 +759,7 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
   // more efficiently. Support vector types. Cleanup code by using m_OneUse.
 
   // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion.
-  Value *A = nullptr; ConstantInt *Cst = nullptr;
+  Value *A = nullptr;
   if (Src->hasOneUse() &&
       match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) {
     // We have three types to worry about here, the type of A, the source of
@@ -843,6 +844,38 @@ Instruction *InstCombiner::visitTrunc(TruncInst &CI) {
   if (Instruction *I = foldVecTruncToExtElt(CI, *this))
     return I;
 
+  // Whenever an element is extracted from a vector, and then truncated,
+  // canonicalize by converting it to a bitcast followed by an
+  // extractelement.
+  //
+  // Example (little endian):
+  //   trunc (extractelement <4 x i64> %X, 0) to i32
+  //   --->
+  //   extractelement <8 x i32> (bitcast <4 x i64> %X to <8 x i32>), i32 0
+  Value *VecOp;
+  if (match(Src,
+            m_OneUse(m_ExtractElement(m_Value(VecOp), m_ConstantInt(Cst))))) {
+    Type *VecOpTy = VecOp->getType();
+    unsigned DestScalarSize = DestTy->getScalarSizeInBits();
+    unsigned VecOpScalarSize = VecOpTy->getScalarSizeInBits();
+    unsigned VecNumElts = VecOpTy->getVectorNumElements();
+
+    // A badly fit destination size would result in an invalid cast.
+    if (VecOpScalarSize % DestScalarSize == 0) {
+      uint64_t TruncRatio = VecOpScalarSize / DestScalarSize;
+      uint64_t BitCastNumElts = VecNumElts * TruncRatio;
+      uint64_t VecOpIdx = Cst->getZExtValue();
+      uint64_t NewIdx = DL.isBigEndian() ? (VecOpIdx + 1) * TruncRatio - 1
+                                         : VecOpIdx * TruncRatio;
+      assert(BitCastNumElts <= std::numeric_limits<uint32_t>::max() &&
+             "overflow 32-bits");
+
+      Type *BitCastTo = VectorType::get(DestTy, BitCastNumElts);
+      Value *BitCast = Builder.CreateBitCast(VecOp, BitCastTo);
+      return ExtractElementInst::Create(BitCast, Builder.getInt32(NewIdx));
+    }
+  }
+
   return nullptr;
 }
 
diff --git a/llvm/test/Transforms/InstCombine/ExtractCast.ll b/llvm/test/Transforms/InstCombine/ExtractCast.ll
index 91df102..9dc9396 100644
--- a/llvm/test/Transforms/InstCombine/ExtractCast.ll
+++ b/llvm/test/Transforms/InstCombine/ExtractCast.ll
@@ -3,8 +3,8 @@
 
 define i32 @a(<4 x i64> %I) {
 ; CHECK-LABEL: @a(
-; CHECK-NEXT:    [[TMP1:%.*]] = extractelement <4 x i64> [[I:%.*]], i32 3
-; CHECK-NEXT:    [[K:%.*]] = trunc i64 [[TMP1]] to i32
+; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <4 x i64> [[I:%.*]] to <8 x i32>
+; CHECK-NEXT:    [[K:%.*]] = extractelement <8 x i32> [[TMP1]], i32 6
 ; CHECK-NEXT:    ret i32 [[K]]
 ;
   %J = trunc <4 x i64> %I to <4 x i32>
diff --git a/llvm/test/Transforms/InstCombine/trunc-extractelement.ll b/llvm/test/Transforms/InstCombine/trunc-extractelement.ll
index 9f4ff5d..c44577d 100644
--- a/llvm/test/Transforms/InstCombine/trunc-extractelement.ll
+++ b/llvm/test/Transforms/InstCombine/trunc-extractelement.ll
@@ -3,10 +3,15 @@
 ; RUN: opt < %s -instcombine -S -data-layout="E" | FileCheck %s --check-prefixes=ANY,BE
 
 define i32 @shrinkExtractElt_i64_to_i32_0(<3 x i64> %x) {
-; ANY-LABEL: @shrinkExtractElt_i64_to_i32_0(
-; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i32 0
-; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
-; ANY-NEXT:    ret i32 [[T]]
+; LE-LABEL: @shrinkExtractElt_i64_to_i32_0(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <6 x i32>
+; LE-NEXT:    [[T:%.*]] = extractelement <6 x i32> [[TMP1]], i32 0
+; LE-NEXT:    ret i32 [[T]]
+;
+; BE-LABEL: @shrinkExtractElt_i64_to_i32_0(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <6 x i32>
+; BE-NEXT:    [[T:%.*]] = extractelement <6 x i32> [[TMP1]], i32 1
+; BE-NEXT:    ret i32 [[T]]
 ;
   %e = extractelement <3 x i64> %x, i32 0
   %t = trunc i64 %e to i32
@@ -14,10 +19,15 @@ define i32 @shrinkExtractElt_i64_to_i32_0(<3 x i64> %x) {
 }
 
 define i32 @shrinkExtractElt_i64_to_i32_1(<3 x i64> %x) {
-; ANY-LABEL: @shrinkExtractElt_i64_to_i32_1(
-; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i32 1
-; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
-; ANY-NEXT:    ret i32 [[T]]
+; LE-LABEL: @shrinkExtractElt_i64_to_i32_1(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <6 x i32>
+; LE-NEXT:    [[T:%.*]] = extractelement <6 x i32> [[TMP1]], i32 2
+; LE-NEXT:    ret i32 [[T]]
+;
+; BE-LABEL: @shrinkExtractElt_i64_to_i32_1(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <6 x i32>
+; BE-NEXT:    [[T:%.*]] = extractelement <6 x i32> [[TMP1]], i32 3
+; BE-NEXT:    ret i32 [[T]]
 ;
   %e = extractelement <3 x i64> %x, i32 1
   %t = trunc i64 %e to i32
@@ -25,10 +35,15 @@ define i32 @shrinkExtractElt_i64_to_i32_1(<3 x i64> %x) {
 }
 
 define i32 @shrinkExtractElt_i64_to_i32_2(<3 x i64> %x) {
-; ANY-LABEL: @shrinkExtractElt_i64_to_i32_2(
-; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i32 2
-; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
-; ANY-NEXT:    ret i32 [[T]]
+; LE-LABEL: @shrinkExtractElt_i64_to_i32_2(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <6 x i32>
+; LE-NEXT:    [[T:%.*]] = extractelement <6 x i32> [[TMP1]], i32 4
+; LE-NEXT:    ret i32 [[T]]
+;
+; BE-LABEL: @shrinkExtractElt_i64_to_i32_2(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <6 x i32>
+; BE-NEXT:    [[T:%.*]] = extractelement <6 x i32> [[TMP1]], i32 5
+; BE-NEXT:    ret i32 [[T]]
 ;
   %e = extractelement <3 x i64> %x, i32 2
   %t = trunc i64 %e to i32
@@ -36,10 +51,15 @@ define i32 @shrinkExtractElt_i64_to_i32_2(<3 x i64> %x) {
 }
 
 define i16 @shrinkExtractElt_i64_to_i16_0(<3 x i64> %x) {
-; ANY-LABEL: @shrinkExtractElt_i64_to_i16_0(
-; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i16 0
-; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i16
-; ANY-NEXT:    ret i16 [[T]]
+; LE-LABEL: @shrinkExtractElt_i64_to_i16_0(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <12 x i16>
+; LE-NEXT:    [[T:%.*]] = extractelement <12 x i16> [[TMP1]], i32 0
+; LE-NEXT:    ret i16 [[T]]
+;
+; BE-LABEL: @shrinkExtractElt_i64_to_i16_0(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <12 x i16>
+; BE-NEXT:    [[T:%.*]] = extractelement <12 x i16> [[TMP1]], i32 3
+; BE-NEXT:    ret i16 [[T]]
 ;
   %e = extractelement <3 x i64> %x, i16 0
   %t = trunc i64 %e to i16
@@ -47,10 +67,15 @@ define i16 @shrinkExtractElt_i64_to_i16_0(<3 x i64> %x) {
 }
 
 define i16 @shrinkExtractElt_i64_to_i16_1(<3 x i64> %x) {
-; ANY-LABEL: @shrinkExtractElt_i64_to_i16_1(
-; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i16 1
-; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i16
-; ANY-NEXT:    ret i16 [[T]]
+; LE-LABEL: @shrinkExtractElt_i64_to_i16_1(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <12 x i16>
+; LE-NEXT:    [[T:%.*]] = extractelement <12 x i16> [[TMP1]], i32 4
+; LE-NEXT:    ret i16 [[T]]
+;
+; BE-LABEL: @shrinkExtractElt_i64_to_i16_1(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <12 x i16>
+; BE-NEXT:    [[T:%.*]] = extractelement <12 x i16> [[TMP1]], i32 7
+; BE-NEXT:    ret i16 [[T]]
 ;
   %e = extractelement <3 x i64> %x, i16 1
   %t = trunc i64 %e to i16
@@ -58,10 +83,15 @@ define i16 @shrinkExtractElt_i64_to_i16_1(<3 x i64> %x) {
 }
 
 define i16 @shrinkExtractElt_i64_to_i16_2(<3 x i64> %x) {
-; ANY-LABEL: @shrinkExtractElt_i64_to_i16_2(
-; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i64> [[X:%.*]], i16 2
-; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i16
-; ANY-NEXT:    ret i16 [[T]]
+; LE-LABEL: @shrinkExtractElt_i64_to_i16_2(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <12 x i16>
+; LE-NEXT:    [[T:%.*]] = extractelement <12 x i16> [[TMP1]], i32 8
+; LE-NEXT:    ret i16 [[T]]
+;
+; BE-LABEL: @shrinkExtractElt_i64_to_i16_2(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i64> [[X:%.*]] to <12 x i16>
+; BE-NEXT:    [[T:%.*]] = extractelement <12 x i16> [[TMP1]], i32 11
+; BE-NEXT:    ret i16 [[T]]
 ;
   %e = extractelement <3 x i64> %x, i16 2
   %t = trunc i64 %e to i16
@@ -70,10 +100,15 @@ define i16 @shrinkExtractElt_i64_to_i16_2(<3 x i64> %x) {
 
 ; Crazy types may be ok.
 define i11 @shrinkExtractElt_i33_to_11_2(<3 x i33> %x) {
-; ANY-LABEL: @shrinkExtractElt_i33_to_11_2(
-; ANY-NEXT:    [[E:%.*]] = extractelement <3 x i33> [[X:%.*]], i16 2
-; ANY-NEXT:    [[T:%.*]] = trunc i33 [[E]] to i11
-; ANY-NEXT:    ret i11 [[T]]
+; LE-LABEL: @shrinkExtractElt_i33_to_11_2(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i33> [[X:%.*]] to <9 x i11>
+; LE-NEXT:    [[T:%.*]] = extractelement <9 x i11> [[TMP1]], i32 6
+; LE-NEXT:    ret i11 [[T]]
+;
+; BE-LABEL: @shrinkExtractElt_i33_to_11_2(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <3 x i33> [[X:%.*]] to <9 x i11>
+; BE-NEXT:    [[T:%.*]] = extractelement <9 x i11> [[TMP1]], i32 8
+; BE-NEXT:    ret i11 [[T]]
 ;
   %e = extractelement <3 x i33> %x, i16 2
   %t = trunc i33 %e to i11
@@ -122,13 +157,17 @@ define i16 @shrinkExtractElt_i64_to_i16_2_extra_use(<3 x i64> %x) {
 
 ; Check to ensure PR45314 remains fixed.
 define <4 x i64> @PR45314(<4 x i64> %x) {
-; ANY-LABEL: @PR45314(
-; ANY-NEXT:    [[E:%.*]] = extractelement <4 x i64> [[X:%.*]], i32 0
-; ANY-NEXT:    [[T:%.*]] = trunc i64 [[E]] to i32
-; ANY-NEXT:    [[I:%.*]] = insertelement <8 x i32> undef, i32 [[T]], i32 0
-; ANY-NEXT:    [[S:%.*]] = shufflevector <8 x i32> [[I]], <8 x i32> undef, <8 x i32> zeroinitializer
-; ANY-NEXT:    [[B:%.*]] = bitcast <8 x i32> [[S]] to <4 x i64>
-; ANY-NEXT:    ret <4 x i64> [[B]]
+; LE-LABEL: @PR45314(
+; LE-NEXT:    [[TMP1:%.*]] = bitcast <4 x i64> [[X:%.*]] to <8 x i32>
+; LE-NEXT:    [[S:%.*]] = shufflevector <8 x i32> [[TMP1]], <8 x i32> undef, <8 x i32> zeroinitializer
+; LE-NEXT:    [[B:%.*]] = bitcast <8 x i32> [[S]] to <4 x i64>
+; LE-NEXT:    ret <4 x i64> [[B]]
+;
+; BE-LABEL: @PR45314(
+; BE-NEXT:    [[TMP1:%.*]] = bitcast <4 x i64> [[X:%.*]] to <8 x i32>
+; BE-NEXT:    [[S:%.*]] = shufflevector <8 x i32> [[TMP1]], <8 x i32> undef, <8 x i32> <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
+; BE-NEXT:    [[B:%.*]] = bitcast <8 x i32> [[S]] to <4 x i64>
+; BE-NEXT:    ret <4 x i64> [[B]]
 ;
   %e = extractelement <4 x i64> %x, i32 0
   %t = trunc i64 %e to i32