[InstCombine] Support sext in foldLogicCastConstant

This adds support for sext in foldLogicCastConstant. This is a prerequisite for D36214.

Differential Revision: https://reviews.llvm.org/D36234

llvm-svn: 309880

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -1089,10 +1089,10 @@ static Instruction *foldLogicCastConstant(BinaryOperator &Logic, CastInst *Cast,
   Type *DestTy = Logic.getType();
   Type *SrcTy = Cast->getSrcTy();
 
-  // Move the logic operation ahead of a zext if the constant is unchanged in
+  // Move the logic operation ahead of a zext or sext if the constant is
-  // the smaller source type. Performing the logic in a smaller type may provide
+  // unchanged in the smaller source type. Performing the logic in a smaller
-  // more information to later folds, and the smaller logic instruction may be
+  // type may provide more information to later folds, and the smaller logic
-  // cheaper (particularly in the case of vectors).
+  // instruction may be cheaper (particularly in the case of vectors).
   Value *X;
   if (match(Cast, m_OneUse(m_ZExt(m_Value(X))))) {
     Constant *TruncC = ConstantExpr::getTrunc(C, SrcTy);
@@ -1104,6 +1104,16 @@ static Instruction *foldLogicCastConstant(BinaryOperator &Logic, CastInst *Cast,
     }
   }
 
+  if (match(Cast, m_OneUse(m_SExt(m_Value(X))))) {
+    Constant *TruncC = ConstantExpr::getTrunc(C, SrcTy);
+    Constant *SextTruncC = ConstantExpr::getSExt(TruncC, DestTy);
+    if (SextTruncC == C) {
+      // LogicOpc (sext X), C --> sext (LogicOpc X, C)
+      Value *NewOp = Builder.CreateBinOp(LogicOpc, X, TruncC);
+      return new SExtInst(NewOp, DestTy);
+    }
+  }
+
   return nullptr;
 }
 

llvm/test/Transforms/InstCombine/cast.ll

@@ -587,9 +587,9 @@ define i64 @test46(i64 %A) {
 
 define i64 @test47(i8 %A) {
 ; CHECK-LABEL: @test47(
-; CHECK-NEXT:    [[B:%.*]] = sext i8 %A to i64
+; CHECK-NEXT:    [[TMP1:%.*]] = or i8 [[A:%.*]], 42
-; CHECK-NEXT:    [[C:%.*]] = and i64 [[B]], 4294967253
+; CHECK-NEXT:    [[C:%.*]] = sext i8 [[TMP1]] to i64
-; CHECK-NEXT:    [[E:%.*]] = or i64 [[C]], 42
+; CHECK-NEXT:    [[E:%.*]] = and i64 [[C]], 4294967295
 ; CHECK-NEXT:    ret i64 [[E]]
 ;
   %B = sext i8 %A to i32

llvm/test/Transforms/InstCombine/logical-select.ll

@@ -504,11 +504,11 @@ define <4 x i32> @vec_sel_xor(<4 x i32> %a, <4 x i32> %b, <4 x i1> %c) {
 
 define <4 x i32> @vec_sel_xor_multi_use(<4 x i32> %a, <4 x i32> %b, <4 x i1> %c) {
 ; CHECK-LABEL: @vec_sel_xor_multi_use(
-; CHECK-NEXT:    [[MASK:%.*]] = sext <4 x i1> %c to <4 x i32>
+; CHECK-NEXT:    [[TMP1:%.*]] = xor <4 x i1> [[C:%.*]], <i1 true, i1 false, i1 false, i1 false>
-; CHECK-NEXT:    [[MASK_FLIP1:%.*]] = xor <4 x i32> [[MASK]], <i32 -1, i32 0, i32 0, i32 0>
+; CHECK-NEXT:    [[MASK_FLIP1:%.*]] = sext <4 x i1> [[TMP1]] to <4 x i32>
-; CHECK-NEXT:    [[TMP1:%.*]] = xor <4 x i1> %c, <i1 false, i1 true, i1 true, i1 true>
+; CHECK-NEXT:    [[TMP2:%.*]] = xor <4 x i1> [[C]], <i1 false, i1 true, i1 true, i1 true>
-; CHECK-NEXT:    [[TMP2:%.*]] = select <4 x i1> [[TMP1]], <4 x i32> %a, <4 x i32> %b
+; CHECK-NEXT:    [[TMP3:%.*]] = select <4 x i1> [[TMP2]], <4 x i32> [[A:%.*]], <4 x i32> [[B:%.*]]
-; CHECK-NEXT:    [[ADD:%.*]] = add <4 x i32> [[TMP2]], [[MASK_FLIP1]]
+; CHECK-NEXT:    [[ADD:%.*]] = add <4 x i32> [[TMP3]], [[MASK_FLIP1]]
 ; CHECK-NEXT:    ret <4 x i32> [[ADD]]
 ;
   %mask = sext <4 x i1> %c to <4 x i32>

llvm/test/Transforms/SLPVectorizer/X86/minimum-sizes.ll

@@ -48,12 +48,12 @@ entry:
 ;        optimization, we make the proposed smaller type (i8) larger (i16) to
 ;        ensure correctness.
 ;
-; CHECK: %[[S0:.+]] = sext <2 x i8> {{.*}} to <2 x i16>
+; CHECK: %[[OR:.+]] = or <2 x i8> {{.*}}, <i8 1, i8 1>
-; CHECK: %[[OR:.+]] = or <2 x i16> %[[S0]], <i16 1, i16 1>
+; CHECK: %[[S0:.+]] = sext <2 x i8> %[[OR]] to <2 x i16>
-; CHECK: %[[E0:.+]] = extractelement <2 x i16> %[[OR]], i32 0
+; CHECK: %[[E0:.+]] = extractelement <2 x i16> %[[S0]], i32 0
 ; CHECK: %[[S1:.+]] = sext i16 %[[E0]] to i64
 ; CHECK: getelementptr inbounds i8, i8* %ptr, i64 %[[S1]]
-; CHECK: %[[E1:.+]] = extractelement <2 x i16> %[[OR]], i32 1
+; CHECK: %[[E1:.+]] = extractelement <2 x i16> %[[S0]], i32 1
 ; CHECK: %[[S2:.+]] = sext i16 %[[E1]] to i64
 ; CHECK: getelementptr inbounds i8, i8* %ptr, i64 %[[S2]]
 ;