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Start allocating stack space at [ebp-4] to not overwrite the return address.

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Also make all loads & stores 4-byte aligned for performance. ;)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4982 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Misha Brukman 2002-12-13 04:34:02 +00:00
parent 07e376bd0d
commit cea2245f04
1 changed files with 9 additions and 2 deletions
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11
lib/CodeGen/RegAllocSimple.cpp
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@ -50,13 +50,15 @@ namespace {
RegAllocSimple(TargetMachine &tm) : TM(tm), CurrMBB(0), maxOffset(0),
RegInfo(tm.getRegisterInfo()),
NumBytesAllocated(0), ByteAlignment(4)
ByteAlignment(4)
{
// build reverse mapping for physReg -> register class
RegInfo->buildReg2RegClassMap(PhysReg2RegClassMap);
RegsUsed[RegInfo->getFramePointer()] = 1;
RegsUsed[RegInfo->getStackPointer()] = 1;
cleanupAfterFunction();
}
bool isAvailableReg(unsigned Reg) {
@ -80,7 +82,7 @@ namespace {
void cleanupAfterFunction() {
RegMap.clear();
SSA2PhysRegMap.clear();
NumBytesAllocated = 0;
NumBytesAllocated = 4;
}
/// Moves value from memory into that register
@ -112,6 +114,7 @@ unsigned RegAllocSimple::allocateStackSpaceFor(unsigned VirtReg,
const TargetRegisterClass *regClass)
{
if (RegMap.find(VirtReg) == RegMap.end()) {
#if 0
unsigned size = regClass->getDataSize();
unsigned over = NumBytesAllocated - (NumBytesAllocated % ByteAlignment);
if (size >= ByteAlignment - over) {
@ -120,6 +123,10 @@ unsigned RegAllocSimple::allocateStackSpaceFor(unsigned VirtReg,
}
RegMap[VirtReg] = NumBytesAllocated;
NumBytesAllocated += size;
#endif
// FIXME: forcing each arg to take 4 bytes on the stack
RegMap[VirtReg] = NumBytesAllocated;
NumBytesAllocated += 4;
}
return RegMap[VirtReg];
}