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Make DSE much more aggressive by performing DCE earlier. Update a testcase to reflect this increased aggressiveness.

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llvm-svn: 46542
This commit is contained in:
Owen Anderson 2008-01-30 01:24:47 +00:00
parent 7d21431939
commit ad9a347656
2 changed files with 56 additions and 3 deletions
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57
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -152,7 +152,7 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
possiblyDead.insert(D);
if (Instruction* D = dyn_cast<Instruction>(last->getOperand(1)))
possiblyDead.insert(D);
last->eraseFromParent();
NumFastStores++;
deletedStore = true;
@ -303,7 +303,7 @@ bool DSE::handleEndBlock(BasicBlock& BB,
MD.removeInstruction(M);
// DCE instructions only used to calculate that memcpy
if (Instruction* D = dyn_cast<Instruction>(M->getSource()))
if (Instruction* D = dyn_cast<Instruction>(M->getRawSource()))
possiblyDead.insert(D);
if (Instruction* D = dyn_cast<Instruction>(M->getLength()))
possiblyDead.insert(D);
@ -325,11 +325,45 @@ bool DSE::handleEndBlock(BasicBlock& BB,
// If we encounter a use of the pointer, it is no longer considered dead
if (LoadInst* L = dyn_cast<LoadInst>(BBI)) {
// However, if this load is unused, we can go ahead and remove it, and
// not have to worry about it making our pointer undead!
if (L->getNumUses() == 0) {
MD.removeInstruction(L);
// DCE instructions only used to calculate that load
if (Instruction* D = dyn_cast<Instruction>(L->getPointerOperand()))
possiblyDead.insert(D);
BBI++;
L->eraseFromParent();
NumFastOther++;
MadeChange = true;
possiblyDead.remove(L);
continue;
}
killPointer = L->getPointerOperand();
} else if (VAArgInst* V = dyn_cast<VAArgInst>(BBI)) {
killPointer = V->getOperand(0);
} else if (AllocaInst* A = dyn_cast<AllocaInst>(BBI)) {
deadPointers.erase(A);
// Dead alloca's can be DCE'd when we reach them
if (A->getNumUses() == 0) {
MD.removeInstruction(A);
// DCE instructions only used to calculate that load
if (Instruction* D = dyn_cast<Instruction>(A->getArraySize()))
possiblyDead.insert(D);
BBI++;
A->eraseFromParent();
NumFastOther++;
MadeChange = true;
possiblyDead.remove(A);
}
continue;
} else if (CallSite::get(BBI).getInstruction() != 0) {
// If this call does not access memory, it can't
@ -383,6 +417,25 @@ bool DSE::handleEndBlock(BasicBlock& BB,
deadPointers.erase(*I);
continue;
} else {
// For any non-memory-affecting non-terminators, DCE them as we reach them
Instruction *CI = BBI;
if (!CI->isTerminator() && CI->getNumUses() == 0) {
// DCE instructions only used to calculate that load
for (Instruction::op_iterator OI = CI->op_begin(), OE = CI->op_end();
OI != OE; ++OI)
if (Instruction* D = dyn_cast<Instruction>(OI))
possiblyDead.insert(D);
BBI++;
CI->eraseFromParent();
NumFastOther++;
MadeChange = true;
possiblyDead.remove(CI);
continue;
}
}
if (!killPointer)

2
test/Transforms/DeadStoreElimination/memcpy.ll
View File

@ -1,4 +1,4 @@
; RUN: llvm-as < %s | opt -dse | llvm-dis | not grep tmp180
; RUN: llvm-as < %s | opt -dse | llvm-dis | not grep alloca
; ModuleID = 'placeholder.adb'
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
target triple = "i686-pc-linux-gnu"