[llvm] 5feeced - [TypePromotion] Fix sext vs zext in promoted constant

[David Green via llvm-commits]

Author: David Green
Date: 2022-05-11T10:47:44+01:00
New Revision: 5feeceddb2b5422dcb555b6d601e35a2d7840707

URL: https://github.com/llvm/llvm-project/commit/5feeceddb2b5422dcb555b6d601e35a2d7840707
DIFF: https://github.com/llvm/llvm-project/commit/5feeceddb2b5422dcb555b6d601e35a2d7840707.diff

LOG: [TypePromotion] Fix sext vs zext in promoted constant

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

Differential Revision: https://reviews.llvm.org/D125294

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/TypePromotion.cpp b/llvm/lib/CodeGen/TypePromotion.cpp
index 6b991aa73de94..fa7c797c70f09 100644
--- a/llvm/lib/CodeGen/TypePromotion.cpp
+++ b/llvm/lib/CodeGen/TypePromotion.cpp
@@ -484,7 +484,7 @@ void IRPromoter::PromoteTree() {
         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);

diff  --git a/llvm/test/Transforms/TypePromotion/ARM/icmps.ll b/llvm/test/Transforms/TypePromotion/ARM/icmps.ll
index 7aa1e7dbc4e5c..880ea18f43882 100644
--- a/llvm/test/Transforms/TypePromotion/ARM/icmps.ll
+++ b/llvm/test/Transforms/TypePromotion/ARM/icmps.ll
@@ -348,3 +348,16 @@ if.then:
 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
+}