[PATCH] D67411: [InstSimplify] simplifyUnsignedRangeCheck(): handle more cases (PR43251)

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri updated this revision to Diff 219720.
lebedev.ri marked an inline comment as done.
lebedev.ri added a comment.

Rebased to only contain the actual change itself and none of the `SimplifyQuery` threading-in.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67411/new/

https://reviews.llvm.org/D67411

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/result-of-usub-by-nonzero-is-non-zero-and-no-overflow.ll


Index: llvm/test/Transforms/InstSimplify/result-of-usub-by-nonzero-is-non-zero-and-no-overflow.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/result-of-usub-by-nonzero-is-non-zero-and-no-overflow.ll
+++ llvm/test/Transforms/InstSimplify/result-of-usub-by-nonzero-is-non-zero-and-no-overflow.ll
@@ -10,9 +10,7 @@
 ; CHECK-NEXT:    [[OFFSET:%.*]] = ptrtoint i64* [[OFFSETPTR:%.*]] to i64
 ; CHECK-NEXT:    [[ADJUSTED:%.*]] = sub i64 [[BASE:%.*]], [[OFFSET]]
 ; CHECK-NEXT:    [[NO_UNDERFLOW:%.*]] = icmp uge i64 [[ADJUSTED]], [[BASE]]
-; CHECK-NEXT:    [[NOT_NULL:%.*]] = icmp ne i64 [[ADJUSTED]], 0
-; CHECK-NEXT:    [[R:%.*]] = and i1 [[NOT_NULL]], [[NO_UNDERFLOW]]
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 [[NO_UNDERFLOW]]
 ;
   %offset = ptrtoint i64* %offsetptr to i64
 
@@ -28,9 +26,7 @@
 ; CHECK-NEXT:    [[OFFSET:%.*]] = ptrtoint i64* [[OFFSETPTR:%.*]] to i64
 ; CHECK-NEXT:    [[ADJUSTED:%.*]] = sub i64 [[BASE:%.*]], [[OFFSET]]
 ; CHECK-NEXT:    [[NO_UNDERFLOW:%.*]] = icmp ult i64 [[ADJUSTED]], [[BASE]]
-; CHECK-NEXT:    [[NOT_NULL:%.*]] = icmp eq i64 [[ADJUSTED]], 0
-; CHECK-NEXT:    [[R:%.*]] = or i1 [[NOT_NULL]], [[NO_UNDERFLOW]]
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 [[NO_UNDERFLOW]]
 ;
   %offset = ptrtoint i64* %offsetptr to i64
 
@@ -46,9 +42,7 @@
 ; CHECK-NEXT:    [[OFFSET:%.*]] = ptrtoint i64* [[OFFSETPTR:%.*]] to i64
 ; CHECK-NEXT:    [[ADJUSTED:%.*]] = sub i64 [[BASE:%.*]], [[OFFSET]]
 ; CHECK-NEXT:    [[NO_UNDERFLOW:%.*]] = icmp ule i64 [[BASE]], [[ADJUSTED]]
-; CHECK-NEXT:    [[NOT_NULL:%.*]] = icmp ne i64 [[ADJUSTED]], 0
-; CHECK-NEXT:    [[R:%.*]] = and i1 [[NOT_NULL]], [[NO_UNDERFLOW]]
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 [[NO_UNDERFLOW]]
 ;
   %offset = ptrtoint i64* %offsetptr to i64
 
@@ -64,9 +58,7 @@
 ; CHECK-NEXT:    [[OFFSET:%.*]] = ptrtoint i64* [[OFFSETPTR:%.*]] to i64
 ; CHECK-NEXT:    [[ADJUSTED:%.*]] = sub i64 [[BASE:%.*]], [[OFFSET]]
 ; CHECK-NEXT:    [[NO_UNDERFLOW:%.*]] = icmp ugt i64 [[BASE]], [[ADJUSTED]]
-; CHECK-NEXT:    [[NOT_NULL:%.*]] = icmp eq i64 [[ADJUSTED]], 0
-; CHECK-NEXT:    [[R:%.*]] = or i1 [[NOT_NULL]], [[NO_UNDERFLOW]]
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 [[NO_UNDERFLOW]]
 ;
   %offset = ptrtoint i64* %offsetptr to i64
 
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1381,6 +1381,26 @@
     return nullptr;
 
   ICmpInst::Predicate UnsignedPred;
+
+  // Y = (A - B);  Y >= A && Y != 0  --> Y >= A  iff B != 0
+  // Y = (A - B);  Y <  A || Y == 0  --> Y <  A  iff B != 0
+  Value *A, *B;
+  if (match(Y, m_Sub(m_Value(A), m_Value(B))) &&
+      match(UnsignedICmp,
+            m_c_ICmp(UnsignedPred, m_Specific(Y), m_Specific(A)))) {
+    if (UnsignedICmp->getOperand(0) != Y)
+      UnsignedPred = ICmpInst::getSwappedPredicate(UnsignedPred);
+
+    if (UnsignedPred == ICmpInst::ICMP_UGE && IsAnd &&
+        EqPred == ICmpInst::ICMP_NE &&
+        isKnownNonZero(B, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
+      return UnsignedICmp;
+    if (UnsignedPred == ICmpInst::ICMP_ULT && !IsAnd &&
+        EqPred == ICmpInst::ICMP_EQ &&
+        isKnownNonZero(B, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
+      return UnsignedICmp;
+  }
+
   if (match(UnsignedICmp, m_ICmp(UnsignedPred, m_Value(X), m_Specific(Y))) &&
       ICmpInst::isUnsigned(UnsignedPred))
     ;


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