[PATCH] D125294: [TypePromotion] Fix sext vs zext in promoted constant

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: craig.topper, samparker, SjoerdMeijer.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
dmgreen requested review of this revision.
Herald added a project: LLVM.

As pointed out in #55342, given non-canonical IR with multiple constants, we check the second operand in isSafeWrap, but can promote both with sext. Fix that as suggested by @craig.topper by ensuring we only extend the second constant if multiple are present.


https://reviews.llvm.org/D125294

Files:
  llvm/lib/CodeGen/TypePromotion.cpp
  llvm/test/Transforms/TypePromotion/ARM/icmps.ll


Index: llvm/test/Transforms/TypePromotion/ARM/icmps.ll
===================================================================
--- llvm/test/Transforms/TypePromotion/ARM/icmps.ll
+++ llvm/test/Transforms/TypePromotion/ARM/icmps.ll
@@ -348,3 +348,16 @@
 if.end:
   ret void
 }
+
+define i32 @degenerateicmp() {
+; CHECK-LABEL: @degenerateicmp(
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 190, 0
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ugt i32 225, [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 1, i32 0
+; CHECK-NEXT:    ret i32 [[TMP3]]
+;
+  %1 = sub i8 -66, 0
+  %2 = icmp ugt i8 -31, %1
+  %3 = select i1 %2, i32 1, i32 0
+  ret i32 %3
+}
Index: llvm/lib/CodeGen/TypePromotion.cpp
===================================================================
--- llvm/lib/CodeGen/TypePromotion.cpp
+++ llvm/lib/CodeGen/TypePromotion.cpp
@@ -484,7 +484,7 @@
         continue;
 
       if (auto *Const = dyn_cast<ConstantInt>(Op)) {
-        Constant *NewConst = SafeWrap.contains(I)
+        Constant *NewConst = (SafeWrap.contains(I) && i == 1)
                                  ? ConstantExpr::getSExt(Const, ExtTy)
                                  : ConstantExpr::getZExt(Const, ExtTy);
         I->setOperand(i, NewConst);


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