[llvm] 45ff287 - [ConstraintSystem] Fix signed overflow in negate.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Tue Dec 3 13:07:05 PST 2024
Author: Florian Hahn
Date: 2024-12-03T21:06:36Z
New Revision: 45ff28746f5f6350a95d8d9a3e3b3a62b932bce9
URL: https://github.com/llvm/llvm-project/commit/45ff28746f5f6350a95d8d9a3e3b3a62b932bce9
DIFF: https://github.com/llvm/llvm-project/commit/45ff28746f5f6350a95d8d9a3e3b3a62b932bce9.diff
LOG: [ConstraintSystem] Fix signed overflow in negate.
Use AddOverflow for potentially overflowing addition to fixed signed
integer overflow.
Compile-time impact is in the noise
https://llvm-compile-time-tracker.com/compare.php?from=bfb26202e05ee2932b4368b5fca607df01e8247f&to=195b0707148b567c674235e59712458e7ce1bb0e&stat=instructions:u
Added:
Modified:
llvm/include/llvm/Analysis/ConstraintSystem.h
llvm/test/Transforms/ConstraintElimination/constraint-overflow.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Analysis/ConstraintSystem.h b/llvm/include/llvm/Analysis/ConstraintSystem.h
index 449852343964ca..01eeadb17db9f0 100644
--- a/llvm/include/llvm/Analysis/ConstraintSystem.h
+++ b/llvm/include/llvm/Analysis/ConstraintSystem.h
@@ -113,7 +113,9 @@ class ConstraintSystem {
static SmallVector<int64_t, 8> negate(SmallVector<int64_t, 8> R) {
// The negated constraint R is obtained by multiplying by -1 and adding 1 to
// the constant.
- R[0] += 1;
+ if (AddOverflow(R[0], int64_t(1), R[0]))
+ return {};
+
return negateOrEqual(R);
}
diff --git a/llvm/test/Transforms/ConstraintElimination/constraint-overflow.ll b/llvm/test/Transforms/ConstraintElimination/constraint-overflow.ll
index 88f87f4afab286..57b7b11be0cf1f 100644
--- a/llvm/test/Transforms/ConstraintElimination/constraint-overflow.ll
+++ b/llvm/test/Transforms/ConstraintElimination/constraint-overflow.ll
@@ -38,3 +38,17 @@ exit:
}
declare void @llvm.assume(i1)
+
+define i1 @negate_overflow_add_1(i64 %x) {
+; CHECK-LABEL: define i1 @negate_overflow_add_1(
+; CHECK-SAME: i64 [[X:%.*]]) {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUB:%.*]] = add nsw i64 [[X]], -9223372036854775807
+; CHECK-NEXT: [[C:%.*]] = icmp slt i64 0, [[SUB]]
+; CHECK-NEXT: ret i1 [[C]]
+;
+entry:
+ %sub = add nsw i64 %x, -9223372036854775807
+ %c = icmp slt i64 0, %sub
+ ret i1 %c
+}
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