maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Fix PR6165. The bug was that LHSKnownZero was being and'd with DemandedMask 

when it should have been and'd with LowBits.  Fix that and while there beef
up the logic in the case of a negative LHS.

llvm-svn: 94745
This commit is contained in:
Duncan Sands 2010-01-28 17:22:42 +00:00
parent 2cb941642e
commit 3a48b87c54
2 changed files with 31 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
View File

@ -681,10 +681,19 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
LHSKnownZero, LHSKnownOne, Depth+1))
return I;
if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits))
LHSKnownZero |= ~LowBits;
// The low bits of LHS are unchanged by the srem.
KnownZero |= LHSKnownZero & LowBits;
KnownOne |= LHSKnownOne & LowBits;
KnownZero |= LHSKnownZero & DemandedMask;
// If LHS is non-negative or has all low bits zero, then the upper bits
// are all zero.
if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits))
KnownZero |= ~LowBits;
// If LHS is negative and not all low bits are zero, then the upper bits
// are all one.
if (LHSKnownOne[BitWidth-1] && ((LHSKnownOne & LowBits) != 0))
KnownOne |= ~LowBits;
assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?");
}

19
llvm/test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
; PR6165
define i32 @f() {
entry:
br label %BB1
BB1: ; preds = %BB1, %entry
; CHECK: BB1:
%x = phi i32 [ -29, %entry ], [ 0, %BB1 ] ; <i32> [#uses=2]
%rem = srem i32 %x, 2 ; <i32> [#uses=1]
%t = icmp eq i32 %rem, -1 ; <i1> [#uses=1]
br i1 %t, label %BB2, label %BB1
; CHECK-NOT: br i1 false
BB2: ; preds = %BB1
; CHECK: BB2:
ret i32 %x
}