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Implement a trivial form of store->load forwarding where the store and the

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load are exactly consequtive.  This is picked up by other passes, but this
triggers thousands of times in fortran programs that use static locals
(and is thus a compile-time speedup).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23320 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-09-12 22:00:15 +00:00
parent 598fbf756f
commit 62f254df04
1 changed files with 9 additions and 0 deletions
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9
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4925,6 +4925,15 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
// None of the following transforms are legal for volatile loads.
if (LI.isVolatile()) return 0;
// If the instruction immediately before this is a store to the same address,
// do a simple form of store->load forwarding.
if (&LI.getParent()->front() != &LI) {
BasicBlock::iterator BBI = &LI; --BBI;
if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
if (SI->getOperand(1) == LI.getOperand(0))
return ReplaceInstUsesWith(LI, SI->getOperand(0));
}
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op))
if (isa<ConstantPointerNull>(GEPI->getOperand(0)) ||