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Teach the X86 backend about unreachable and undef. Among other things, we

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now compile:

'foo() {}' into "ret" instead of "mov EAX, 0; ret"


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17049 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-10-16 18:13:05 +00:00
parent a9d12c0a56
commit 30483b0c84
1 changed files with 15 additions and 1 deletions
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16
lib/Target/X86/X86ISelSimple.cpp
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@ -175,6 +175,7 @@ namespace {
// Control flow operators
void visitReturnInst(ReturnInst &RI);
void visitBranchInst(BranchInst &BI);
void visitUnreachableInst(UnreachableInst &UI) {}
struct ValueRecord {
Value *Val;
@ -447,7 +448,20 @@ unsigned X86ISel::getFixedSizedAllocaFI(AllocaInst *AI) {
void X86ISel::copyConstantToRegister(MachineBasicBlock *MBB,
MachineBasicBlock::iterator IP,
Constant *C, unsigned R) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
if (isa<UndefValue>(C)) {
switch (getClassB(C->getType())) {
case cFP:
// FIXME: SHOULD TEACH STACKIFIER ABOUT UNDEF VALUES!
BuildMI(*MBB, IP, X86::FLD0, 0, R);
return;
case cLong:
BuildMI(*MBB, IP, X86::IMPLICIT_DEF, 0, R+1);
// FALL THROUGH
default:
BuildMI(*MBB, IP, X86::IMPLICIT_DEF, 0, R);
return;
}
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
unsigned Class = 0;
switch (CE->getOpcode()) {
case Instruction::GetElementPtr: