[PATCH] D144248: [InstCombine] canonicalize urem as cmp+select (part 2)

[Allen zhong via Phabricator via llvm-commits]

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Address the dominating condition.
Fix https://github.com/llvm/llvm-project/issues/60546


https://reviews.llvm.org/D144248

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstCombine/urem-via-cmp-select.ll


Index: llvm/test/Transforms/InstCombine/urem-via-cmp-select.ll
===================================================================
--- llvm/test/Transforms/InstCombine/urem-via-cmp-select.ll
+++ llvm/test/Transforms/InstCombine/urem-via-cmp-select.ll
@@ -108,13 +108,39 @@
   ret i64 %out
 }
 
-; TODO: https://alive2.llvm.org/ce/z/eHkgRa
+; https://alive2.llvm.org/ce/z/eHkgRa
 define noundef i8 @urem_with_dominating_condition(i8 %x, i8 %n) {
 ; CHECK-LABEL: @urem_with_dominating_condition(
 ; CHECK-NEXT:  start:
-; CHECK-NEXT:    [[COND:%.*]] = icmp ult i8 [[X:%.*]], [[N:%.*]]
+; CHECK-NEXT:    [[X_FR:%.*]] = freeze i8 [[X:%.*]]
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i8 [[X_FR]], [[N:%.*]]
 ; CHECK-NEXT:    br i1 [[COND]], label [[DOTBB0:%.*]], label [[DOTBB1:%.*]]
 ; CHECK:       .bb0:
+; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[X_FR]], 1
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp eq i8 [[ADD]], [[N]]
+; CHECK-NEXT:    [[OUT:%.*]] = select i1 [[TMP0]], i8 0, i8 [[ADD]]
+; CHECK-NEXT:    ret i8 [[OUT]]
+; CHECK:       .bb1:
+; CHECK-NEXT:    ret i8 0
+;
+start:
+  %cond = icmp ult i8 %x, %n
+  br i1 %cond, label %.bb0, label %.bb1 ; Should also works for a dominating condition
+.bb0:
+  %add = add i8 %x, 1
+  %out = urem i8 %add, %n
+  ret i8 %out
+.bb1:
+  ret i8 0
+}
+
+; Negative test
+define noundef i8 @urem_with_opposite_condition(i8 %x, i8 %n) {
+; CHECK-LABEL: @urem_with_opposite_condition(
+; CHECK-NEXT:  start:
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i8 [[X:%.*]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[COND]], label [[DOTBB1:%.*]], label [[DOTBB0:%.*]]
+; CHECK:       .bb0:
 ; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[X]], 1
 ; CHECK-NEXT:    [[OUT:%.*]] = urem i8 [[ADD]], [[N]]
 ; CHECK-NEXT:    ret i8 [[OUT]]
@@ -123,7 +149,7 @@
 ;
 start:
   %cond = icmp ult i8 %x, %n
-  br i1 %cond, label %.bb0, label %.bb1 ; Should also works for a dominating condition
+  br i1 %cond, label %.bb1, label %.bb0 ; Revert the condition
 .bb0:
   %add = add i8 %x, 1
   %out = urem i8 %add, %n
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -3913,6 +3913,11 @@
   if (Value *V = simplifyICmpWithDominatingAssume(Pred, LHS, RHS, Q))
     return V;
 
+  std::optional<bool> Checked =
+      isImpliedByDomCondition(Pred, LHS, RHS, Q.CxtI, Q.DL);
+  if (Checked && *Checked == true)
+    return getTrue(ITy);
+
   // Simplify comparisons of related pointers using a powerful, recursive
   // GEP-walk when we have target data available..
   if (LHS->getType()->isPointerTy())


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