[llvm] 62ae7d9 - [LoopUnroll] Fix missing sign extension

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2024-02-01T16:08:25+01:00
New Revision: 62ae7d976f494f3dbd297331b19cd1204750de6f

URL: https://github.com/llvm/llvm-project/commit/62ae7d976f494f3dbd297331b19cd1204750de6f
DIFF: https://github.com/llvm/llvm-project/commit/62ae7d976f494f3dbd297331b19cd1204750de6f.diff

LOG: [LoopUnroll] Fix missing sign extension

For integers larger than 64-bit, this would zero-extend a -1
value, instead of sign-extending it.

Fixes https://github.com/llvm/llvm-project/issues/80289.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
    llvm/test/Transforms/LoopUnroll/runtime-i128.ll

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 612f699708814..650f055356c07 100644
--- a/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -776,7 +776,7 @@ bool llvm::UnrollRuntimeLoopRemainder(
       !isGuaranteedNotToBeUndefOrPoison(TripCount, AC, PreHeaderBR, DT)) {
     TripCount = B.CreateFreeze(TripCount);
     BECount =
-        B.CreateAdd(TripCount, ConstantInt::get(TripCount->getType(), -1));
+        B.CreateAdd(TripCount, Constant::getAllOnesValue(TripCount->getType()));
   } else {
     // If we don't need to freeze, use SCEVExpander for BECount as well, to
     // allow slightly better value reuse.

diff  --git a/llvm/test/Transforms/LoopUnroll/runtime-i128.ll b/llvm/test/Transforms/LoopUnroll/runtime-i128.ll
index 50e09beddb37a..4cd8e7ca5d16f 100644
--- a/llvm/test/Transforms/LoopUnroll/runtime-i128.ll
+++ b/llvm/test/Transforms/LoopUnroll/runtime-i128.ll
@@ -8,7 +8,7 @@ define void @test(i128 %n, i128 %m) {
 ; CHECK-SAME: i128 [[N:%.*]], i128 [[M:%.*]]) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP0:%.*]] = freeze i128 [[N]]
-; CHECK-NEXT:    [[TMP1:%.*]] = add i128 [[TMP0]], 18446744073709551615
+; CHECK-NEXT:    [[TMP1:%.*]] = add i128 [[TMP0]], -1
 ; CHECK-NEXT:    [[XTRAITER:%.*]] = and i128 [[TMP0]], 7
 ; CHECK-NEXT:    [[TMP2:%.*]] = icmp ult i128 [[TMP1]], 7
 ; CHECK-NEXT:    br i1 [[TMP2]], label [[EXIT_UNR_LCSSA:%.*]], label [[ENTRY_NEW:%.*]]