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6bb4958543
The DAGCombiner created a negative shiftamount, stored in an unsigned variable. Later the optimizer eliminated the shift entirely as being undefined. Example: (srl (shl X, 56) 48). ShiftAmt is 4294967288. Fix it by checking that the shiftamount is positive, and storing in a signed variable. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72331 91177308-0d34-0410-b5e6-96231b3b80d8
15 lines
588 B
LLVM
15 lines
588 B
LLVM
; RUN: llvm-as < %s | llc | grep -E {sar|shl|mov|or} | count 4
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; Check that the shr(shl X, 56), 48) is not mistakenly turned into
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; a shr (X, -8) that gets subsequently "optimized away" as undef
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; PR4254
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
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target triple = "x86_64-unknown-linux-gnu"
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define i64 @foo(i64 %b) nounwind readnone {
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entry:
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%shl = shl i64 %b, 56 ; <i64> [#uses=1]
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%shr = ashr i64 %shl, 48 ; <i64> [#uses=1]
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%add5 = or i64 %shr, 1 ; <i64> [#uses=1]
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ret i64 %add5
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}
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