6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-09-27 00:21:03 +00:00
Code Issues Projects Releases Wiki Activity

Added inst combine tarnsform for (1 << X) & C pattrens where C is (some PowerOf2 - 1)

Browse Source 
This patch can handles following cases from http://nondot.org/sabre/LLVMNotes/InstCombine.txt
  "((1 << X) & 7) == 0" ==> "X > 2"
  "((1 << X) & 7) != 0" ==> "X < 3".

Differential Revision: http://reviews.llvm.org/D3678



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210007 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dinesh Dwivedi
2014-06-02 07:57:24 +00:00
parent c469e543a0
commit bcc4bce6b7
2 changed files with 41 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@@ -2540,7 +2540,7 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// bit is set. If the comparison is against zero, then this is a check
// to see if *that* bit is set.
APInt Op0KnownZeroInverted = ~Op0KnownZero;
if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
if (~Op1KnownZero == 0) {
// If the LHS is an AND with the same constant, look through it.
Value *LHS = nullptr;
ConstantInt *LHSC = nullptr;
@@ -2550,11 +2550,19 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) == 0" into "x != 3".
// or turn "((1 << x)&7) == 0" into "x > 2".
Value *X = nullptr;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_NE, X,
ConstantInt::get(X->getType(), CmpVal));
APInt ValToCheck = Op0KnownZeroInverted;
if (ValToCheck.isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_NE, X,
ConstantInt::get(X->getType(), CmpVal));
} else if ((++ValToCheck).isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros() - 1;
return new ICmpInst(ICmpInst::ICMP_UGT, X,
ConstantInt::get(X->getType(), CmpVal));
}
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,
@@ -2577,7 +2585,7 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// bit is set. If the comparison is against zero, then this is a check
// to see if *that* bit is set.
APInt Op0KnownZeroInverted = ~Op0KnownZero;
if (~Op1KnownZero == 0 && Op0KnownZeroInverted.isPowerOf2()) {
if (~Op1KnownZero == 0) {
// If the LHS is an AND with the same constant, look through it.
Value *LHS = nullptr;
ConstantInt *LHSC = nullptr;
@@ -2587,11 +2595,19 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// If the LHS is 1 << x, and we know the result is a power of 2 like 8,
// then turn "((1 << x)&8) != 0" into "x == 3".
// or turn "((1 << x)&7) != 0" into "x < 3".
Value *X = nullptr;
if (match(LHS, m_Shl(m_One(), m_Value(X)))) {
unsigned CmpVal = Op0KnownZeroInverted.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_EQ, X,
ConstantInt::get(X->getType(), CmpVal));
APInt ValToCheck = Op0KnownZeroInverted;
if (ValToCheck.isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_EQ, X,
ConstantInt::get(X->getType(), CmpVal));
} else if ((++ValToCheck).isPowerOf2()) {
unsigned CmpVal = ValToCheck.countTrailingZeros();
return new ICmpInst(ICmpInst::ICMP_ULT, X,
ConstantInt::get(X->getType(), CmpVal));
}
}
// If the LHS is 8 >>u x, and we know the result is a power of 2 like 1,