Allow overlaps between virtreg and physreg live ranges.
The RegisterCoalescer understands overlapping live ranges where one
register is defined as a copy of the other. With this change, register
allocators using LiveRegMatrix can do the same, at least for copies
between physical and virtual registers.
When a physreg is defined by a copy from a virtreg, allow those live
ranges to overlap:
%CL<def> = COPY %vreg11:sub_8bit; GR32_ABCD:%vreg11
%vreg13<def,tied1> = SAR32rCL %vreg13<tied0>, %CL<imp-use,kill>
We can assign %vreg11 to %ECX, overlapping the live range of %CL.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163336 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveInterval.cpp b/lib/CodeGen/LiveInterval.cpp
index 0a795e6..50e181c 100644
--- a/lib/CodeGen/LiveInterval.cpp
+++ b/lib/CodeGen/LiveInterval.cpp
@@ -27,6 +27,7 @@
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetRegisterInfo.h"
+#include "RegisterCoalescer.h"
#include <algorithm>
using namespace llvm;
@@ -142,6 +143,48 @@
return false;
}
+bool LiveInterval::overlaps(const LiveInterval &Other,
+ const CoalescerPair &CP,
+ const SlotIndexes &Indexes) const {
+ assert(!empty() && "empty interval");
+ if (Other.empty())
+ return false;
+
+ // Use binary searches to find initial positions.
+ const_iterator I = find(Other.beginIndex());
+ const_iterator IE = end();
+ if (I == IE)
+ return false;
+ const_iterator J = Other.find(I->start);
+ const_iterator JE = Other.end();
+ if (J == JE)
+ return false;
+
+ for (;;) {
+ // J has just been advanced to satisfy:
+ assert(J->end >= I->start);
+ // Check for an overlap.
+ if (J->start < I->end) {
+ // I and J are overlapping. Find the later start.
+ SlotIndex Def = std::max(I->start, J->start);
+ // Allow the overlap if Def is a coalescable copy.
+ if (Def.isBlock() ||
+ !CP.isCoalescable(Indexes.getInstructionFromIndex(Def)))
+ return true;
+ }
+ // Advance the iterator that ends first to check for more overlaps.
+ if (J->end > I->end) {
+ std::swap(I, J);
+ std::swap(IE, JE);
+ }
+ // Advance J until J->end >= I->start.
+ do
+ if (++J == JE)
+ return false;
+ while (J->end < I->start);
+ }
+}
+
/// overlaps - Return true if the live interval overlaps a range specified
/// by [Start, End).
bool LiveInterval::overlaps(SlotIndex Start, SlotIndex End) const {