diff options
| -rw-r--r-- | llvm/test/Transforms/SimplifyCFG/signbit-like-value-extension.ll | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/llvm/test/Transforms/SimplifyCFG/signbit-like-value-extension.ll b/llvm/test/Transforms/SimplifyCFG/signbit-like-value-extension.ll new file mode 100644 index 00000000000..ea013ef9e6c --- /dev/null +++ b/llvm/test/Transforms/SimplifyCFG/signbit-like-value-extension.ll @@ -0,0 +1,39 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt < %s -simplifycfg -S | FileCheck %s + +; This looks like a normal sign extension, but it's not. +; This comes up in JPEG decoding. This check is really unpredictable, +; so it is likely beneficial to avoid the branch. + +define i32 @extend_value(i32 %storage, i32 %nbits) { +; CHECK-LABEL: @extend_value( +; CHECK-NEXT: bb: +; CHECK-NEXT: [[SKIPNBITS:%.*]] = sub i32 32, [[NBITS:%.*]] +; CHECK-NEXT: [[VALUE:%.*]] = lshr i32 [[STORAGE:%.*]], [[SKIPNBITS]] +; CHECK-NEXT: [[SHOULDEXTEND:%.*]] = icmp sgt i32 [[STORAGE]], -1 +; CHECK-NEXT: br i1 [[SHOULDEXTEND]], label [[EXTEND:%.*]], label [[END:%.*]] +; CHECK: extend: +; CHECK-NEXT: [[HIGHBITMASK:%.*]] = shl nsw i32 -1, [[NBITS]] +; CHECK-NEXT: [[HIGHBITMASKPLUSONE:%.*]] = add nsw i32 [[HIGHBITMASK]], 1 +; CHECK-NEXT: [[EXTENDED:%.*]] = add i32 [[HIGHBITMASKPLUSONE]], [[VALUE]] +; CHECK-NEXT: br label [[END]] +; CHECK: end: +; CHECK-NEXT: [[RES:%.*]] = phi i32 [ [[EXTENDED]], [[EXTEND]] ], [ [[VALUE]], [[BB:%.*]] ] +; CHECK-NEXT: ret i32 [[RES]] +; +bb: + %skipnbits = sub i32 32, %nbits + %value = lshr i32 %storage, %skipnbits + %shouldextend = icmp sgt i32 %storage, -1 + br i1 %shouldextend, label %extend, label %end + +extend: ; preds = %bb + %highbitmask = shl nsw i32 -1, %nbits + %highbitmaskplusone = add nsw i32 %highbitmask, 1 + %extended = add i32 %highbitmaskplusone, %value + br label %end + +end: ; preds = %extend, %bb + %res = phi i32 [ %extended, %extend ], [ %value, %bb ] + ret i32 %res +} |
