[PATCH] D38934: Move folding of icmp with zero after checking for min/max idioms.

[Artur Gainullin via Phabricator via llvm-commits]

ArturGainullin updated this revision to Diff 119069.
ArturGainullin added a comment.

Fixed comment.


https://reviews.llvm.org/D38934

Files:
  lib/Transforms/InstCombine/InstCombineCompares.cpp
  lib/Transforms/InstCombine/InstCombineInternal.h
  test/Transforms/InstCombine/minmax-fold.ll


Index: test/Transforms/InstCombine/minmax-fold.ll
===================================================================
--- test/Transforms/InstCombine/minmax-fold.ll
+++ test/Transforms/InstCombine/minmax-fold.ll
@@ -507,7 +507,7 @@
 ; CHECK-LABEL: @clamp_check_for_no_infinite_loop1(
 ; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 [[I:%.*]], 255
 ; CHECK-NEXT:    [[SEL1:%.*]] = select i1 [[CMP1]], i32 [[I]], i32 255
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[I]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[SEL1]], 0
 ; CHECK-NEXT:    [[RES:%.*]] = select i1 [[TMP1]], i32 [[SEL1]], i32 0
 ; CHECK-NEXT:    ret i32 [[RES]]
 ;
Index: lib/Transforms/InstCombine/InstCombineInternal.h
===================================================================
--- lib/Transforms/InstCombine/InstCombineInternal.h
+++ lib/Transforms/InstCombine/InstCombineInternal.h
@@ -700,6 +700,7 @@
   Instruction *foldICmpInstWithConstantNotInt(ICmpInst &Cmp);
   Instruction *foldICmpBinOp(ICmpInst &Cmp);
   Instruction *foldICmpEquality(ICmpInst &Cmp);
+  Instruction *foldICmpWithZero(ICmpInst &Cmp);
 
   Instruction *foldICmpSelectConstant(ICmpInst &Cmp, SelectInst *Select,
                                       ConstantInt *C);
Index: lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1318,6 +1318,24 @@
   return ExtractValueInst::Create(Call, 1, "sadd.overflow");
 }
 
+// Handle (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
+Instruction *InstCombiner::foldICmpWithZero(ICmpInst &Cmp) {
+  CmpInst::Predicate Pred = Cmp.getPredicate();
+  Value *X = Cmp.getOperand(0);
+
+  if (match(Cmp.getOperand(1), m_Zero()) && Pred == ICmpInst::ICMP_SGT) {
+    Value *A, *B;
+    SelectPatternResult SPR = matchSelectPattern(X, A, B);
+    if (SPR.Flavor == SPF_SMIN) {
+      if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
+        return new ICmpInst(Pred, B, Cmp.getOperand(1));
+      if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
+        return new ICmpInst(Pred, A, Cmp.getOperand(1));
+    }
+  }
+  return nullptr;
+}
+
 // Fold icmp Pred X, C.
 Instruction *InstCombiner::foldICmpWithConstant(ICmpInst &Cmp) {
   CmpInst::Predicate Pred = Cmp.getPredicate();
@@ -1349,17 +1367,6 @@
         return Res;
   }
 
-  // (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0)
-  if (C->isNullValue() && Pred == ICmpInst::ICMP_SGT) {
-    SelectPatternResult SPR = matchSelectPattern(X, A, B);
-    if (SPR.Flavor == SPF_SMIN) {
-      if (isKnownPositive(A, DL, 0, &AC, &Cmp, &DT))
-        return new ICmpInst(Pred, B, Cmp.getOperand(1));
-      if (isKnownPositive(B, DL, 0, &AC, &Cmp, &DT))
-        return new ICmpInst(Pred, A, Cmp.getOperand(1));
-    }
-  }
-
   // FIXME: Use m_APInt to allow folds for splat constants.
   ConstantInt *CI = dyn_cast<ConstantInt>(Cmp.getOperand(1));
   if (!CI)
@@ -4462,6 +4469,10 @@
           (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1))
         return nullptr;
 
+  // Do this after checking for min/max to prevent infinite looping.
+  if (Instruction *Res = foldICmpWithZero(I))
+    return Res;
+
   // FIXME: We only do this after checking for min/max to prevent infinite
   // looping caused by a reverse canonicalization of these patterns for min/max.
   // FIXME: The organization of folds is a mess. These would naturally go into


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D38934.119069.patch
Type: text/x-patch
Size: 3464 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20171015/20535c7f/attachment.bin>