[llvm] [SCCP] Extend `visitBinaryOperator` to overflowing binary ops (PR #84470)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-function-specialization

@llvm/pr-subscribers-llvm-transforms

Author: Antonio Frighetto (antoniofrighetto)

<details>
<summary>Changes</summary>

Leverage more refined ranges results when handling overflowing binary operators.

---
Full diff: https://github.com/llvm/llvm-project/pull/84470.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Utils/SCCPSolver.cpp (+12-1) 
- (modified) llvm/test/Transforms/SCCP/add-nuw-nsw-flags.ll (+29) 


``````````diff
diff --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
index a185e8cd371c60..a0e522d9e555c7 100644
--- a/llvm/lib/Transforms/Utils/SCCPSolver.cpp
+++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
@@ -1486,7 +1486,18 @@ void SCCPInstVisitor::visitBinaryOperator(Instruction &I) {
   // Try to simplify to a constant range.
   ConstantRange A = getConstantRange(V1State, I.getType());
   ConstantRange B = getConstantRange(V2State, I.getType());
-  ConstantRange R = A.binaryOp(cast<BinaryOperator>(&I)->getOpcode(), B);
+
+  auto *BO = cast<BinaryOperator>(&I);
+  ConstantRange R = ConstantRange::getEmpty(I.getType()->getScalarSizeInBits());
+  if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(BO)) {
+    bool HasNUW = OBO->hasNoUnsignedWrap();
+    bool HasNSW = OBO->hasNoSignedWrap();
+    unsigned Flags = (HasNUW ? OverflowingBinaryOperator::NoUnsignedWrap : 0) |
+                     (HasNSW ? OverflowingBinaryOperator::NoSignedWrap : 0);
+    R = A.overflowingBinaryOp(BO->getOpcode(), B, Flags);
+  } else {
+    R = A.binaryOp(BO->getOpcode(), B);
+  }
   mergeInValue(&I, ValueLatticeElement::getRange(R));
 
   // TODO: Currently we do not exploit special values that produce something
diff --git a/llvm/test/Transforms/SCCP/add-nuw-nsw-flags.ll b/llvm/test/Transforms/SCCP/add-nuw-nsw-flags.ll
index b8f5d5dba0c4b2..05d9acd1919629 100644
--- a/llvm/test/Transforms/SCCP/add-nuw-nsw-flags.ll
+++ b/llvm/test/Transforms/SCCP/add-nuw-nsw-flags.ll
@@ -240,3 +240,32 @@ then:
 else:
   ret i16 0
 }
+
+define i1 @test_add_nuw_sub(i32 %a) {
+; CHECK-LABEL: @test_add_nuw_sub(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ADD:%.*]] = add nuw i32 [[A:%.*]], 10000
+; CHECK-NEXT:    [[SUB:%.*]] = add i32 [[ADD]], -5000
+; CHECK-NEXT:    ret i1 false
+;
+entry:
+  %add = add nuw i32 %a, 10000
+  %sub = add i32 %add, -5000
+  %cond = icmp ult i32 %sub, 5000
+  ret i1 %cond
+}
+
+define i1 @test_add_nsw_sub(i32 %a) {
+; CHECK-LABEL: @test_add_nsw_sub(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[ADD:%.*]] = add nsw i32 [[A:%.*]], 10000
+; CHECK-NEXT:    [[SUB:%.*]] = add nsw i32 [[ADD]], -5000
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i32 [[SUB]], 5000
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+entry:
+  %add = add nsw i32 %a, 10000
+  %sub = add i32 %add, -5000
+  %cond = icmp ult i32 %sub, 5000
+  ret i1 %cond
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/84470