[CGP] add another bailout for degenerate code (PR41064)
This is almost the same as:
rL355345
...and should prevent any potential crashing from examples like:
https://bugs.llvm.org/show_bug.cgi?id=41064
...although the bug was masked by:
rL355823
...and I'm not sure how to repro the problem after that change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356218 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenPrepare.cpp b/lib/CodeGen/CodeGenPrepare.cpp
index e70e4ee..e8498eb 100644
--- a/lib/CodeGen/CodeGenPrepare.cpp
+++ b/lib/CodeGen/CodeGenPrepare.cpp
@@ -1267,8 +1267,12 @@
static bool combineToUSubWithOverflow(CmpInst *Cmp, const TargetLowering &TLI,
const DataLayout &DL, DominatorTree &DT,
bool &ModifiedDT) {
- // Convert (A u> B) to (A u< B) to simplify pattern matching.
+ // We are not expecting non-canonical/degenerate code. Just bail out.
Value *A = Cmp->getOperand(0), *B = Cmp->getOperand(1);
+ if (isa<Constant>(A) && isa<Constant>(B))
+ return false;
+
+ // Convert (A u> B) to (A u< B) to simplify pattern matching.
ICmpInst::Predicate Pred = Cmp->getPredicate();
if (Pred == ICmpInst::ICMP_UGT) {
std::swap(A, B);
diff --git a/test/Transforms/CodeGenPrepare/X86/overflow-intrinsics.ll b/test/Transforms/CodeGenPrepare/X86/overflow-intrinsics.ll
index 9a0bf28..a9ec204 100644
--- a/test/Transforms/CodeGenPrepare/X86/overflow-intrinsics.ll
+++ b/test/Transforms/CodeGenPrepare/X86/overflow-intrinsics.ll
@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -codegenprepare -S < %s | FileCheck %s
; RUN: opt -enable-debugify -codegenprepare -S < %s 2>&1 | FileCheck %s -check-prefix=DEBUG
@@ -454,6 +455,26 @@
unreachable
}
+; Similarly for usubo.
+
+define i1 @bar2() {
+; CHECK-LABEL: @bar2(
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 1, 0
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+ %cmp = icmp eq i64 1, 0
+ ret i1 %cmp
+}
+
+define i64 @foo2(i8 *%p) {
+; CHECK-LABEL: @foo2(
+; CHECK-NEXT: [[SUB:%.*]] = add nsw i64 1, -1
+; CHECK-NEXT: ret i64 [[SUB]]
+;
+ %sub = add nsw i64 1, -1
+ ret i64 %sub
+}
+
; Check that every instruction inserted by -codegenprepare has a debug location.
; DEBUG: CheckModuleDebugify: PASS
