[TypePromotion] Fix sext vs zext in promoted constant

[dmgreen]

Summary

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.

Fixes #55342

[samparker]

LGTM, cheers

llvm/lib/CodeGen/TypePromotion.cpp

if (Sinks.count(I))
       continue;
 
     for (unsigned i = 0, e = I->getNumOperands(); i < e; ++i) {
       Value *Op = I->getOperand(i);
       if ((Op->getType() == ExtTy) || !isa<IntegerType>(Op->getType()))
         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);
       } else if (isa<UndefValue>(Op))
         I->setOperand(i, UndefValue::get(ExtTy));
     }
 
     // Mutate the result type, unless this is an icmp or switch.

llvm/test/Transforms/TypePromotion/ARM/icmps.ll

 
 if.then:
   store i32 0, i32* %b, align 4
   br label %if.end
 
 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
+}