[PATCH] D100095: [InstCombine] Conditionally emitting nsw/nuw flags when combining two add operations

[Mehrnoosh Heidarpour via Phabricator via llvm-commits]

MehrHeidar updated this revision to Diff 337397.
MehrHeidar added a comment.

The test case for negative values with `nuw` flag is added.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D100095/new/

https://reviews.llvm.org/D100095

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/icmp-add.ll


Index: llvm/test/Transforms/InstCombine/icmp-add.ll
===================================================================
--- llvm/test/Transforms/InstCombine/icmp-add.ll
+++ llvm/test/Transforms/InstCombine/icmp-add.ll
@@ -666,7 +666,7 @@
 
 define i1 @without_nsw_nuw(i8 %x, i8 %y) {
 ; CHECK-LABEL: @without_nsw_nuw(
-; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i8 [[X:%.*]], 2
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[X:%.*]], 2
 ; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp eq i8 [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i1 [[TOBOOL]]
 ;
@@ -678,7 +678,7 @@
 
 define i1 @with_nsw_nuw(i8 %x, i8 %y) {
 ; CHECK-LABEL: @with_nsw_nuw(
-; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i8 [[X:%.*]], 2
+; CHECK-NEXT:    [[TMP1:%.*]] = add nuw nsw i8 [[X:%.*]], 2
 ; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp eq i8 [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i1 [[TOBOOL]]
 ;
@@ -702,7 +702,7 @@
 
 define i1 @with_nsw_small(i8 %x, i8 %y) {
 ; CHECK-LABEL: @with_nsw_small(
-; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i8 [[Y:%.*]], 2
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y:%.*]], 2
 ; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp eq i8 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[TOBOOL]]
 ;
@@ -714,7 +714,7 @@
 
 define i1 @with_nuw_large(i8 %x, i8 %y) {
 ; CHECK-LABEL: @with_nuw_large(
-; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i8 [[X:%.*]], 2
+; CHECK-NEXT:    [[TMP1:%.*]] = add nuw i8 [[X:%.*]], 2
 ; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp eq i8 [[TMP1]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i1 [[TOBOOL]]
 ;
@@ -726,7 +726,7 @@
 
 define i1 @with_nuw_small(i8 %x, i8 %y) {
 ; CHECK-LABEL: @with_nuw_small(
-; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i8 [[Y:%.*]], 2
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[Y:%.*]], 2
 ; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp eq i8 [[TMP1]], [[X:%.*]]
 ; CHECK-NEXT:    ret i1 [[TOBOOL]]
 ;
@@ -735,3 +735,15 @@
   %tobool = icmp eq i8 %t2, %t1
   ret i1 %tobool
 }
+
+define i1 @with_nuw_large_negative(i8 %x, i8 %y) {
+; CHECK-LABEL: @with_nuw_large_negative(
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[X:%.*]], -2
+; CHECK-NEXT:    [[TOBOOL:%.*]] = icmp eq i8 [[TMP1]], [[Y:%.*]]
+; CHECK-NEXT:    ret i1 [[TOBOOL]]
+;
+  %t1=add nuw i8 %x, -37
+  %t2=add i8 %y, -35
+  %tobool=icmp eq i8 %2, %1
+  ret i1 %tobool
+}
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3917,11 +3917,15 @@
           APInt AP2Abs = C2->getValue().abs();
           if (AP1Abs.uge(AP2Abs)) {
             ConstantInt *C3 = Builder.getInt(AP1 - AP2);
-            Value *NewAdd = Builder.CreateNSWAdd(A, C3);
+            bool HasNUW = BO0->hasNoUnsignedWrap() && C3->getValue().ule(AP1);
+            bool HasNSW = BO0->hasNoSignedWrap();
+            Value *NewAdd = Builder.CreateAdd(A, C3, "", HasNUW, HasNSW);
             return new ICmpInst(Pred, NewAdd, C);
           } else {
             ConstantInt *C3 = Builder.getInt(AP2 - AP1);
-            Value *NewAdd = Builder.CreateNSWAdd(C, C3);
+            bool HasNUW = BO1->hasNoUnsignedWrap() && C3->getValue().ule(AP2);
+            bool HasNSW = BO1->hasNoSignedWrap();
+            Value *NewAdd = Builder.CreateAdd(C, C3, "", HasNUW, HasNSW);
             return new ICmpInst(Pred, A, NewAdd);
           }
         }


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