[PATCH] D157187: [InstCombine] Propagate the nuw/nsw for instruction neg-sub

[Allen zhong via Phabricator via llvm-commits]

Allen created this revision.
Allen added reviewers: arsenm, nikic, goldstein.w.n, RKSimon, efriedma, dmgreen.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
Allen requested review of this revision.
Herald added subscribers: llvm-commits, wdng.
Herald added a project: LLVM.

proofs: https://alive2.llvm.org/ce/z/rncRNQ


https://reviews.llvm.org/D157187

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  llvm/test/Transforms/InstCombine/abs-intrinsic.ll
  llvm/test/Transforms/InstCombine/nsw.ll


Index: llvm/test/Transforms/InstCombine/nsw.ll
===================================================================
--- llvm/test/Transforms/InstCombine/nsw.ll
+++ llvm/test/Transforms/InstCombine/nsw.ll
@@ -145,7 +145,7 @@
 
 define i32 @neg_sub0_sub_nsw_nsw(i32 %a, i32 %b) {
 ; CHECK-LABEL: @neg_sub0_sub_nsw_nsw(
-; CHECK-NEXT:    [[C_NEG:%.*]] = sub i32 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT:    [[C_NEG:%.*]] = sub nsw i32 [[B:%.*]], [[A:%.*]]
 ; CHECK-NEXT:    ret i32 [[C_NEG]]
 ;
   %c = sub nsw i32 %a, %b
@@ -181,7 +181,7 @@
 
 define i32 @neg_mul_sub_nsw_nsw(i32 %a, i32 %b) {
 ; CHECK-LABEL: @neg_mul_sub_nsw_nsw(
-; CHECK-NEXT:    [[C_NEG:%.*]] = sub i32 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT:    [[C_NEG:%.*]] = sub nsw i32 [[B:%.*]], [[A:%.*]]
 ; CHECK-NEXT:    ret i32 [[C_NEG]]
 ;
   %c = sub nsw i32 %a, %b
Index: llvm/test/Transforms/InstCombine/abs-intrinsic.ll
===================================================================
--- llvm/test/Transforms/InstCombine/abs-intrinsic.ll
+++ llvm/test/Transforms/InstCombine/abs-intrinsic.ll
@@ -485,7 +485,7 @@
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
 ; CHECK:       cond.true:
-; CHECK-NEXT:    [[SUB_NEG:%.*]] = sub i32 [[Y]], [[X]]
+; CHECK-NEXT:    [[SUB_NEG:%.*]] = sub nsw i32 [[Y]], [[X]]
 ; CHECK-NEXT:    br label [[COND_END]]
 ; CHECK:       cond.end:
 ; CHECK-NEXT:    [[R:%.*]] = phi i32 [ [[SUB_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
@@ -512,7 +512,7 @@
 ; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP_NOT]], label [[COND_END:%.*]], label [[COND_TRUE:%.*]]
 ; CHECK:       cond.true:
-; CHECK-NEXT:    [[SUB_NEG:%.*]] = sub i32 [[Y]], [[X]]
+; CHECK-NEXT:    [[SUB_NEG:%.*]] = sub nsw i32 [[Y]], [[X]]
 ; CHECK-NEXT:    br label [[COND_END]]
 ; CHECK:       cond.end:
 ; CHECK-NEXT:    [[R:%.*]] = phi i32 [ [[SUB_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
@@ -565,7 +565,7 @@
 ; CHECK-NEXT:    [[CMP_NOT:%.*]] = icmp sgt i8 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP_NOT]], label [[COND_END:%.*]], label [[COND_TRUE:%.*]]
 ; CHECK:       cond.true:
-; CHECK-NEXT:    [[SUB_NEG:%.*]] = sub i8 [[Y]], [[X]]
+; CHECK-NEXT:    [[SUB_NEG:%.*]] = sub nsw i8 [[Y]], [[X]]
 ; CHECK-NEXT:    br label [[COND_END]]
 ; CHECK:       cond.end:
 ; CHECK-NEXT:    [[R:%.*]] = phi i8 [ [[SUB_NEG]], [[COND_TRUE]] ], [ 0, [[ENTRY:%.*]] ]
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -2058,8 +2058,18 @@
                      m_Select(m_Value(), m_Specific(Op1), m_Specific(&I))) ||
                match(UI, m_Select(m_Value(), m_Specific(&I), m_Specific(Op1)));
       })) {
-    if (Value *NegOp1 = Negator::Negate(IsNegation, Op1, *this))
+    if (Value *NegOp1 = Negator::Negate(IsNegation, Op1, *this)) {
+      auto *InstOp1 = dyn_cast<Instruction>(NegOp1);
+      if (InstOp1 && InstOp1->getOpcode() == Instruction::Sub &&
+          isa<Instruction>(Op1) && IsNegation) {
+        auto *Op1Inst = cast<Instruction>(Op1);
+        if (I.hasNoUnsignedWrap() && Op1Inst->hasNoUnsignedWrap())
+          InstOp1->setHasNoUnsignedWrap();
+        if (I.hasNoSignedWrap() && Op1Inst->hasNoSignedWrap())
+          InstOp1->setHasNoSignedWrap();
+      }
       return BinaryOperator::CreateAdd(NegOp1, Op0);
+    }
   }
   if (IsNegation)
     return TryToNarrowDeduceFlags(); // Should have been handled in Negator!


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