36 lines
1.5 KiB
LLVM
36 lines
1.5 KiB
LLVM
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
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; This looks like a normal sign extension, but it's not.
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; This comes up in JPEG decoding. This check is really unpredictable,
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; so it is likely beneficial to avoid the branch.
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define i32 @extend_value(i32 %storage, i32 %nbits) {
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; CHECK-LABEL: @extend_value(
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; CHECK-NEXT: bb:
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; CHECK-NEXT: [[SKIPNBITS:%.*]] = sub i32 32, [[NBITS:%.*]]
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; CHECK-NEXT: [[VALUE:%.*]] = lshr i32 [[STORAGE:%.*]], [[SKIPNBITS]]
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; CHECK-NEXT: [[SHOULDEXTEND:%.*]] = icmp sgt i32 [[STORAGE]], -1
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; CHECK-NEXT: [[HIGHBITMASK:%.*]] = shl nsw i32 -1, [[NBITS]]
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; CHECK-NEXT: [[HIGHBITMASKPLUSONE:%.*]] = add nsw i32 [[HIGHBITMASK]], 1
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; CHECK-NEXT: [[EXTENDED:%.*]] = add i32 [[HIGHBITMASKPLUSONE]], [[VALUE]]
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; CHECK-NEXT: [[RES:%.*]] = select i1 [[SHOULDEXTEND]], i32 [[EXTENDED]], i32 [[VALUE]]
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; CHECK-NEXT: ret i32 [[RES]]
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;
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bb:
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%skipnbits = sub i32 32, %nbits
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%value = lshr i32 %storage, %skipnbits
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%shouldextend = icmp sgt i32 %storage, -1
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br i1 %shouldextend, label %extend, label %end
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extend: ; preds = %bb
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%highbitmask = shl nsw i32 -1, %nbits
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%highbitmaskplusone = add nsw i32 %highbitmask, 1
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%extended = add i32 %highbitmaskplusone, %value
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br label %end
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end: ; preds = %extend, %bb
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%res = phi i32 [ %extended, %extend ], [ %value, %bb ]
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ret i32 %res
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}
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