Changes in directory llvm/lib/CodeGen:
PHIElimination.cpp updated: 1.40 -> 1.41
---
Log message:
Add support for targets (like Alpha) that have terminator instructions which
use virtual registers. We now allow the first instruction in a block of
terminators to use virtual registers, and update phi elimination to correctly
update livevar when eliminating phi's. This fixes a problem on a testcase
Andrew sent me.
---
Diffs of the changes: (+41 -5)
PHIElimination.cpp | 46 +++++++++++++++++++++++++++++++++++++++++-----
1 files changed, 41 insertions(+), 5 deletions(-)
Index: llvm/lib/CodeGen/PHIElimination.cpp
diff -u llvm/lib/CodeGen/PHIElimination.cpp:1.40
llvm/lib/CodeGen/PHIElimination.cpp:1.41
--- llvm/lib/CodeGen/PHIElimination.cpp:1.40 Wed Jan 4 00:47:48 2006
+++ llvm/lib/CodeGen/PHIElimination.cpp Wed Jan 4 01:12:21 2006
@@ -98,6 +98,17 @@
return true;
}
+/// InstructionUsesRegister - Return true if the specified machine instr has a
+/// use of the specified register.
+static bool InstructionUsesRegister(MachineInstr *MI, unsigned SrcReg) {
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
+ if (MI->getOperand(0).isRegister() &&
+ MI->getOperand(0).getReg() == SrcReg &&
+ MI->getOperand(0).isUse())
+ return true;
+ return false;
+}
+
/// LowerAtomicPHINode - Lower the PHI node at the top of the specified block,
/// under the assuption that it needs to be lowered in a way that supports
/// atomic execution of PHIs. This lowering method is always correct all of
the
@@ -262,12 +273,37 @@
}
// Okay, if we now know that the value is not live out of the block,
- // we can add a kill marker to the copy we inserted saying that it
- // kills the incoming value!
- //
+ // we can add a kill marker in this block saying that it kills the incoming
+ // value!
if (!ValueIsLive) {
- MachineBasicBlock::iterator Prev = prior(I);
- LV->addVirtualRegisterKilled(SrcReg, Prev);
+ // In our final twist, we have to decide which instruction kills the
+ // register. In most cases this is the copy, however, the first
+ // terminator instruction at the end of the block may also use the value.
+ // In this case, we should mark *it* as being the killing block, not the
+ // copy.
+ bool FirstTerminatorUsesValue = false;
+ if (I != opBlock.end()) {
+ FirstTerminatorUsesValue = InstructionUsesRegister(I, SrcReg);
+
+ // Check that no other terminators use values.
+#ifndef NDEBUG
+ for (MachineBasicBlock::iterator TI = next(I); TI != opBlock.end();
+ ++TI) {
+ assert(!InstructionUsesRegister(TI, SrcReg) &&
+ "Terminator instructions cannot use virtual registers unless"
+ "they are the first terminator in a block!");
+ }
+#endif
+ }
+
+ MachineBasicBlock::iterator KillInst;
+ if (!FirstTerminatorUsesValue)
+ KillInst = prior(I);
+ else
+ KillInst = I;
+
+ // Finally, mark it killed.
+ LV->addVirtualRegisterKilled(SrcReg, KillInst);
// This vreg no longer lives all of the way through opBlock.
unsigned opBlockNum = opBlock.getNumber();
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