From: Sanjay Patel <spatel@rotateright.com>
Date: Wed, 21 Aug 2019 11:56:08 +0000 (+0000)
Subject: [InstCombine] narrow icmp with extended operands of different widths
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fdfa6e242302ba90b9cc2f64a010a7bec5b3f27e;p=llvm

[InstCombine] narrow icmp with extended operands of different widths

An intermediate extend is used to widen the narrow operand to the width of
the other (wider) operand. At that point, we have the same logic as the
existing transform that was restricted to folds of equal width zext/sext.

This mostly solves PR42700:
https://bugs.llvm.org/show_bug.cgi?id=42700

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@369519 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index b318d0b2de9..5e0a3c37979 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4026,7 +4026,8 @@ Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
   return nullptr;
 }
 
-static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp) {
+static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp,
+                                           InstCombiner::BuilderTy &Builder) {
   assert(isa<CastInst>(ICmp.getOperand(0)) && "Expected cast for operand 0");
   auto *CastOp0 = cast<CastInst>(ICmp.getOperand(0));
   Value *X;
@@ -4038,15 +4039,25 @@ static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp) {
   if (auto *CastOp1 = dyn_cast<CastInst>(ICmp.getOperand(1))) {
     // If the signedness of the two casts doesn't agree (i.e. one is a sext
     // and the other is a zext), then we can't handle this.
+    // TODO: This is too strict. We can handle some predicates (equality?).
     if (CastOp0->getOpcode() != CastOp1->getOpcode())
       return nullptr;
 
     // Not an extension from the same type?
-    // TODO: Handle this by extending the narrower operand to the type of
-    //       the wider operand.
     Value *Y = CastOp1->getOperand(0);
-    if (X->getType() != Y->getType())
-      return nullptr;
+    Type *XTy = X->getType(), *YTy = Y->getType();
+    if (XTy != YTy) {
+      // One of the casts must have one use because we are creating a new cast.
+      if (!CastOp0->hasOneUse() && !CastOp1->hasOneUse())
+        return nullptr;
+      // Extend the narrower operand to the type of the wider operand.
+      if (XTy->getScalarSizeInBits() < YTy->getScalarSizeInBits())
+        X = Builder.CreateCast(CastOp0->getOpcode(), X, YTy);
+      else if (YTy->getScalarSizeInBits() < XTy->getScalarSizeInBits())
+        Y = Builder.CreateCast(CastOp0->getOpcode(), Y, XTy);
+      else
+        return nullptr;
+    }
 
     // (zext X) == (zext Y) --> X == Y
     // (sext X) == (sext Y) --> X == Y
@@ -4148,7 +4159,7 @@ Instruction *InstCombiner::foldICmpWithCastOp(ICmpInst &ICmp) {
       return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
   }
 
-  return foldICmpWithZextOrSext(ICmp);
+  return foldICmpWithZextOrSext(ICmp, Builder);
 }
 
 static bool isNeutralValue(Instruction::BinaryOps BinaryOp, Value *RHS) {
diff --git a/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll b/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll
index f5a0c1c259d..170114fb48d 100644
--- a/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll
+++ b/test/Transforms/InstCombine/2004-11-27-SetCCForCastLargerAndConstant.ll
@@ -269,9 +269,8 @@ define i1 @gt_unsigned_to_small_negative(i8 %SB) {
 
 define i1 @different_size_zext_zext_ugt(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_zext_zext_ugt(
-; CHECK-NEXT:    [[ZX:%.*]] = zext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[ZY:%.*]] = zext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp ugt i25 [[ZX]], [[ZY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zx = zext i7 %x to i25
@@ -282,9 +281,8 @@ define i1 @different_size_zext_zext_ugt(i7 %x, i4 %y) {
 
 define <2 x i1> @different_size_zext_zext_ugt_commute(<2 x i4> %x, <2 x i7> %y) {
 ; CHECK-LABEL: @different_size_zext_zext_ugt_commute(
-; CHECK-NEXT:    [[ZX:%.*]] = zext <2 x i4> [[X:%.*]] to <2 x i25>
-; CHECK-NEXT:    [[ZY:%.*]] = zext <2 x i7> [[Y:%.*]] to <2 x i25>
-; CHECK-NEXT:    [[R:%.*]] = icmp ugt <2 x i25> [[ZX]], [[ZY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext <2 x i4> [[X:%.*]] to <2 x i7>
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt <2 x i7> [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i1> [[R]]
 ;
   %zx = zext <2 x i4> %x to <2 x i25>
@@ -295,9 +293,8 @@ define <2 x i1> @different_size_zext_zext_ugt_commute(<2 x i4> %x, <2 x i7> %y)
 
 define i1 @different_size_zext_zext_ult(i4 %x, i7 %y) {
 ; CHECK-LABEL: @different_size_zext_zext_ult(
-; CHECK-NEXT:    [[ZX:%.*]] = zext i4 [[X:%.*]] to i25
-; CHECK-NEXT:    [[ZY:%.*]] = zext i7 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp ult i25 [[ZX]], [[ZY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i4 [[X:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i7 [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zx = zext i4 %x to i25
@@ -308,9 +305,8 @@ define i1 @different_size_zext_zext_ult(i4 %x, i7 %y) {
 
 define i1 @different_size_zext_zext_eq(i4 %x, i7 %y) {
 ; CHECK-LABEL: @different_size_zext_zext_eq(
-; CHECK-NEXT:    [[ZX:%.*]] = zext i4 [[X:%.*]] to i25
-; CHECK-NEXT:    [[ZY:%.*]] = zext i7 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i25 [[ZX]], [[ZY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i4 [[X:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i7 [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zx = zext i4 %x to i25
@@ -321,9 +317,8 @@ define i1 @different_size_zext_zext_eq(i4 %x, i7 %y) {
 
 define i1 @different_size_zext_zext_ne_commute(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_zext_zext_ne_commute(
-; CHECK-NEXT:    [[ZX:%.*]] = zext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[ZY:%.*]] = zext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i25 [[ZX]], [[ZY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zx = zext i7 %x to i25
@@ -334,9 +329,8 @@ define i1 @different_size_zext_zext_ne_commute(i7 %x, i4 %y) {
 
 define i1 @different_size_zext_zext_slt(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_zext_zext_slt(
-; CHECK-NEXT:    [[ZX:%.*]] = zext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[ZY:%.*]] = zext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp ult i25 [[ZX]], [[ZY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zx = zext i7 %x to i25
@@ -347,9 +341,8 @@ define i1 @different_size_zext_zext_slt(i7 %x, i4 %y) {
 
 define i1 @different_size_zext_zext_sgt(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_zext_zext_sgt(
-; CHECK-NEXT:    [[ZX:%.*]] = zext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[ZY:%.*]] = zext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp ugt i25 [[ZX]], [[ZY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp ult i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %zx = zext i7 %x to i25
@@ -360,9 +353,8 @@ define i1 @different_size_zext_zext_sgt(i7 %x, i4 %y) {
 
 define i1 @different_size_sext_sext_sgt(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_sext_sgt(
-; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[SY:%.*]] = sext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp sgt i25 [[SX]], [[SY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp slt i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %sx = sext i7 %x to i25
@@ -373,9 +365,8 @@ define i1 @different_size_sext_sext_sgt(i7 %x, i4 %y) {
 
 define i1 @different_size_sext_sext_sle(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_sext_sle(
-; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[SY:%.*]] = sext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp sle i25 [[SX]], [[SY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp sge i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %sx = sext i7 %x to i25
@@ -386,9 +377,8 @@ define i1 @different_size_sext_sext_sle(i7 %x, i4 %y) {
 
 define i1 @different_size_sext_sext_eq(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_sext_eq(
-; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[SY:%.*]] = sext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i25 [[SX]], [[SY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %sx = sext i7 %x to i25
@@ -399,9 +389,8 @@ define i1 @different_size_sext_sext_eq(i7 %x, i4 %y) {
 
 define i1 @different_size_sext_sext_ule(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_sext_ule(
-; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25
-; CHECK-NEXT:    [[SY:%.*]] = sext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp ule i25 [[SX]], [[SY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %sx = sext i7 %x to i25
@@ -410,6 +399,8 @@ define i1 @different_size_sext_sext_ule(i7 %x, i4 %y) {
   ret i1 %r
 }
 
+; TODO: This can be reduced.
+
 define i1 @different_size_sext_zext_ne(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_zext_ne(
 ; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25
@@ -427,10 +418,10 @@ declare void @use(i25)
 
 define i1 @different_size_sext_sext_ule_extra_use1(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_sext_ule_extra_use1(
-; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25
 ; CHECK-NEXT:    [[SY:%.*]] = sext i4 [[Y:%.*]] to i25
 ; CHECK-NEXT:    call void @use(i25 [[SY]])
-; CHECK-NEXT:    [[R:%.*]] = icmp ule i25 [[SX]], [[SY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i4 [[Y]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i7 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %sx = sext i7 %x to i25
@@ -444,8 +435,8 @@ define i1 @different_size_sext_sext_ule_extra_use2(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_sext_ule_extra_use2(
 ; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25
 ; CHECK-NEXT:    call void @use(i25 [[SX]])
-; CHECK-NEXT:    [[SY:%.*]] = sext i4 [[Y:%.*]] to i25
-; CHECK-NEXT:    [[R:%.*]] = icmp ule i25 [[SX]], [[SY]]
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i4 [[Y:%.*]] to i7
+; CHECK-NEXT:    [[R:%.*]] = icmp uge i7 [[TMP1]], [[X]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %sx = sext i7 %x to i25
@@ -455,6 +446,8 @@ define i1 @different_size_sext_sext_ule_extra_use2(i7 %x, i4 %y) {
   ret i1 %r
 }
 
+; Negative test - extra uses on both casts is too much.
+
 define i1 @different_size_sext_sext_ule_extra_use3(i7 %x, i4 %y) {
 ; CHECK-LABEL: @different_size_sext_sext_ule_extra_use3(
 ; CHECK-NEXT:    [[SX:%.*]] = sext i7 [[X:%.*]] to i25