Teach the X86 backend about unreachable and undef. Among other things, we
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
diff --git a/lib/Target/X86/X86ISelSimple.cpp b/lib/Target/X86/X86ISelSimple.cpp
index a938bae..926492e 100644
--- a/lib/Target/X86/X86ISelSimple.cpp
+++ b/lib/Target/X86/X86ISelSimple.cpp
@@ -175,6 +175,7 @@
// Control flow operators
void visitReturnInst(ReturnInst &RI);
void visitBranchInst(BranchInst &BI);
+ void visitUnreachableInst(UnreachableInst &UI) {}
struct ValueRecord {
Value *Val;
@@ -447,7 +448,20 @@
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: