6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-13 04:30:23 +00:00
Code Issues Projects Releases Wiki Activity

A shift of a power of two is a power of two or zero.

Browse Source 
For completeness - not spotted in the wild.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143211 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2011-10-28 18:30:05 +00:00
parent c65c747bc4
commit 4604fc7791
2 changed files with 16 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
lib/Analysis/ValueTracking.cpp
View File

@ -769,6 +769,12 @@ bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, bool OrZero,
if (Depth++ == MaxDepth)
return false;
Value *X = 0, *Y = 0;
// A shift of a power of two is a power of two or zero.
if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) ||
match(V, m_Shr(m_Value(X), m_Value()))))
return isPowerOfTwo(X, TD, /*OrZero*/true, Depth);
if (ZExtInst *ZI = dyn_cast<ZExtInst>(V))
return isPowerOfTwo(ZI->getOperand(0), TD, OrZero, Depth);
@ -776,7 +782,6 @@ bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, bool OrZero,
return isPowerOfTwo(SI->getTrueValue(), TD, OrZero, Depth) &&
isPowerOfTwo(SI->getFalseValue(), TD, OrZero, Depth);
Value *X = 0, *Y = 0;
if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
// A power of two and'd with anything is a power of two or zero.
if (isPowerOfTwo(X, TD, /*OrZero*/true, Depth) ||

10
test/Transforms/InstSimplify/AndOrXor.ll
View File

@ -10,3 +10,13 @@ define i64 @pow2(i32 %x) {
ret i64 %e2
; CHECK: ret i64 %e
}
define i64 @pow2b(i32 %x) {
; CHECK: @pow2b
%sh = shl i32 2, %x
%e = zext i32 %sh to i64
%nege = sub i64 0, %e
%e2 = and i64 %e, %nege
ret i64 %e2
; CHECK: ret i64 %e
}