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llvm-6502/test/CodeGen/X86/2009-05-23-dagcombine-shifts.ll

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Select an OR with immediate as an ADD if the input bits are known zero. This allow the instruction to be 3address-fied if needed. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93152 91177308-0d34-0410-b5e6-96231b3b80d8
2010-01-11 17:03:47 +00:00
; RUN: llc < %s | FileCheck %s
Fix PR4254. 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
2009-05-23 17:29:48 +00:00
; Check that the shr(shl X, 56), 48) is not mistakenly turned into
; a shr (X, -8) that gets subsequently "optimized away" as undef
; PR4254
Select an OR with immediate as an ADD if the input bits are known zero. This allow the instruction to be 3address-fied if needed. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93152 91177308-0d34-0410-b5e6-96231b3b80d8
2010-01-11 17:03:47 +00:00
Fix PR4254. 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
2009-05-23 17:29:48 +00:00
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"
target triple = "x86_64-unknown-linux-gnu"
define i64 @foo(i64 %b) nounwind readnone {
entry:
Select an OR with immediate as an ADD if the input bits are known zero. This allow the instruction to be 3address-fied if needed. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93152 91177308-0d34-0410-b5e6-96231b3b80d8
2010-01-11 17:03:47 +00:00
; CHECK: foo:
; CHECK: shlq $56, %rdi
; CHECK: sarq $48, %rdi
; CHECK: leaq 1(%rdi), %rax
Fix PR4254. 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
2009-05-23 17:29:48 +00:00
%shl = shl i64 %b, 56 ; <i64> [#uses=1]
%shr = ashr i64 %shl, 48 ; <i64> [#uses=1]
%add5 = or i64 %shr, 1 ; <i64> [#uses=1]
ret i64 %add5
}
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