6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-20 10:30:03 +00:00
Code Issues Projects Releases Wiki Activity

Just mark the sign bit as known zero, rather than any other irrelevant bits

Browse Source 
known zero in the LHS.  Fixes PR12541.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155818 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2012-04-30 11:56:58 +00:00
parent bfbab99b58
commit 5ff30e70f8
2 changed files with 13 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
lib/Analysis/ValueTracking.cpp
View File

@ -564,7 +564,7 @@ void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne,
Depth+1);
// If it's known zero, our sign bit is also zero.
if (LHSKnownZero.isNegative())
KnownZero |= LHSKnownZero;
KnownZero.setBit(BitWidth - 1);
}
break;

12
test/Transforms/InstCombine/2012-04-30-SRem.ll Normal file
View File

@ -0,0 +1,12 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; PR12541
define i32 @foo(i32 %x) {
%y = xor i32 %x, 3
%z = srem i32 1656690544, %y
%sext = shl i32 %z, 24
%s = ashr exact i32 %sext, 24
ret i32 %s
; CHECK-NOT: and
; The shifts were wrongly being turned into an and with 112
}