[RegAllocGreedy] avoid using physreg candidates that cannot be correctly spilled
For the AMDGPU target if a MBB contains exec mask restore preamble, SplitEditor may get state when it cannot insert a spill instruction.
E.g. for a MIR
bb.100:
%1 = S_OR_SAVEEXEC_B64 %2, implicit-def $exec, implicit-def $scc, implicit $exec
and if the regalloc will try to allocate a virtreg to the physreg already assigned to virtreg %1, it should insert spill instruction before the S_OR_SAVEEXEC_B64 instruction.
But it is not possible since can generate incorrect code in terms of exec mask.
The change makes regalloc to ignore such physreg candidates.
Reviewed By: rampitec
Differential Revision: https://reviews.llvm.org/D52052
llvm-svn: 343004
diff --git a/llvm/lib/CodeGen/SplitKit.h b/llvm/lib/CodeGen/SplitKit.h
index 8fbe724..bcc8f8c 100644
--- a/llvm/lib/CodeGen/SplitKit.h
+++ b/llvm/lib/CodeGen/SplitKit.h
@@ -25,6 +25,7 @@
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/LiveInterval.h"
+#include "llvm/CodeGen/LiveIntervals.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/SlotIndexes.h"
@@ -76,6 +77,18 @@
/// Returns the last insert point as an iterator for \pCurLI in \pMBB.
MachineBasicBlock::iterator getLastInsertPointIter(const LiveInterval &CurLI,
MachineBasicBlock &MBB);
+
+ /// Return the base index of the first insert point in \pMBB.
+ SlotIndex getFirstInsertPoint(MachineBasicBlock &MBB) {
+ SlotIndex Res = LIS.getMBBStartIdx(&MBB);
+ if (!MBB.empty()) {
+ MachineBasicBlock::iterator MII = MBB.SkipPHIsLabelsAndDebug(MBB.begin());
+ if (MII != MBB.end())
+ Res = LIS.getInstructionIndex(*MII);
+ }
+ return Res;
+ }
+
};
/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
@@ -225,6 +238,10 @@
MachineBasicBlock::iterator getLastSplitPointIter(MachineBasicBlock *BB) {
return IPA.getLastInsertPointIter(*CurLI, *BB);
}
+
+ SlotIndex getFirstSplitPoint(unsigned Num) {
+ return IPA.getFirstInsertPoint(*MF.getBlockNumbered(Num));
+ }
};
/// SplitEditor - Edit machine code and LiveIntervals for live range