[llvm-commits] CVS: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
Chris Lattner
lattner at cs.uiuc.edu
Sat Sep 17 22:12:21 PDT 2005
Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.374 -> 1.375
---
Log message:
implement shift.ll:test25. This compiles:
struct S { unsigned int i : 6, j : 11, k : 15; } b;
void plus3 (unsigned int x) {
b.k += x;
}
to:
_plus3:
lis r2, ha16(L_b$non_lazy_ptr)
lwz r2, lo16(L_b$non_lazy_ptr)(r2)
lwz r3, 0(r2)
rlwinm r4, r3, 0, 0, 14
add r4, r4, r3
rlwimi r4, r3, 0, 15, 31
stw r4, 0(r2)
blr
instead of:
_plus3:
lis r2, ha16(L_b$non_lazy_ptr)
lwz r2, lo16(L_b$non_lazy_ptr)(r2)
lwz r4, 0(r2)
srwi r5, r4, 17
add r3, r5, r3
slwi r3, r3, 17
rlwimi r3, r4, 0, 15, 31
stw r3, 0(r2)
blr
---
Diffs of the changes: (+53 -3)
InstructionCombining.cpp | 56 ++++++++++++++++++++++++++++++++++++++++++++---
1 files changed, 53 insertions(+), 3 deletions(-)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.374 llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.375
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.374 Sat Sep 17 23:24:45 2005
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Sun Sep 18 00:12:10 2005
@@ -3355,9 +3355,58 @@
}
}
- // If the operand is an bitwise operator with a constant RHS, and the
- // shift is the only use, we can pull it out of the shift.
- if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0))
+ if (BinaryOperator *Op0BO = dyn_cast<BinaryOperator>(Op0)) {
+ // Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
+ switch (Op0BO->getOpcode()) {
+ default: break;
+ case Instruction::Add:
+ case Instruction::And:
+ case Instruction::Or:
+ case Instruction::Xor:
+ // These operators commute.
+ // Turn (Y + (X >> C)) << C -> (X + (Y << C)) & (~0 << C)
+ if (ShiftInst *XS = dyn_cast<ShiftInst>(Op0BO->getOperand(1)))
+ if (isLeftShift && XS->hasOneUse() && XS->getOperand(1) == CUI &&
+ XS->getOpcode() == Instruction::Shr) {
+ break;
+ Instruction *YS = new ShiftInst(Instruction::Shl,
+ Op0BO->getOperand(0), CUI,
+ Op0BO->getName());
+ InsertNewInstBefore(YS, I); // (Y << C)
+ Instruction *X = BinaryOperator::create(Op0BO->getOpcode(), YS,
+ XS->getOperand(0),
+ XS->getName());
+ InsertNewInstBefore(X, I); // (X + (Y << C))
+ Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
+ C2 = ConstantExpr::getShl(C2, CUI);
+ std::cerr << "FOLD1: " << *Op0BO;
+ return BinaryOperator::createAnd(X, C2);
+ }
+ // Fall through.
+ case Instruction::Sub:
+ // Turn ((X >> C) + Y) << C -> (X + (Y << C)) & (~0 << C)
+ if (ShiftInst *XS = dyn_cast<ShiftInst>(Op0BO->getOperand(0)))
+ if (isLeftShift && XS->hasOneUse() && XS->getOperand(1) == CUI &&
+ XS->getOpcode() == Instruction::Shr) {
+ Instruction *YS = new ShiftInst(Instruction::Shl,
+ Op0BO->getOperand(0), CUI,
+ Op0BO->getName());
+ InsertNewInstBefore(YS, I); // (Y << C)
+ Instruction *X = BinaryOperator::create(Op0BO->getOpcode(), YS,
+ XS->getOperand(0),
+ XS->getName());
+ InsertNewInstBefore(X, I); // (X + (Y << C))
+ Constant *C2 = ConstantInt::getAllOnesValue(X->getType());
+ C2 = ConstantExpr::getShl(C2, CUI);
+ std::cerr << "FOLD2: " << *Op0BO;
+ return BinaryOperator::createAnd(X, C2);
+ }
+ break;
+ }
+
+
+ // If the operand is an bitwise operator with a constant RHS, and the
+ // shift is the only use, we can pull it out of the shift.
if (ConstantInt *Op0C = dyn_cast<ConstantInt>(Op0BO->getOperand(1))) {
bool isValid = true; // Valid only for And, Or, Xor
bool highBitSet = false; // Transform if high bit of constant set?
@@ -3400,6 +3449,7 @@
NewRHS);
}
}
+ }
}
// If this is a shift of a shift, see if we can fold the two together...
More information about the llvm-commits
mailing list