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

include/llvm/CodeGen/LiveInterval.h

@@ -29,6 +29,7 @@
 #include <climits>
 
 namespace llvm {
+  class CoalescerPair;
   class LiveIntervals;
   class MachineInstr;
   class MachineRegisterInfo;
@@ -366,6 +367,14 @@ namespace llvm {
       return overlapsFrom(other, other.begin());
     }
 
+    /// overlaps - Return true if the two intervals have overlapping segments
+    /// that are not coalescable according to CP.
+    ///
+    /// Overlapping segments where one interval is defined by a coalescable
+    /// copy are allowed.
+    bool overlaps(const LiveInterval &Other, const CoalescerPair &CP,
+                  const SlotIndexes&) const;
+
     /// overlaps - Return true if the live interval overlaps a range specified
     /// by [Start, End).
     bool overlaps(SlotIndex Start, SlotIndex End) const;

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 @@ bool LiveInterval::overlapsFrom(const LiveInterval& other,
   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 {

lib/CodeGen/LiveRegMatrix.cpp

@@ -13,6 +13,7 @@
 
 #define DEBUG_TYPE "regalloc"
 #include "LiveRegMatrix.h"
+#include "RegisterCoalescer.h"
 #include "VirtRegMap.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -117,8 +118,9 @@ bool LiveRegMatrix::checkRegUnitInterference(LiveInterval &VirtReg,
                                              unsigned PhysReg) {
   if (VirtReg.empty())
     return false;
+  CoalescerPair CP(VirtReg.reg, PhysReg, *TRI);
   for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units)
-    if (VirtReg.overlaps(LIS->getRegUnit(*Units)))
+    if (VirtReg.overlaps(LIS->getRegUnit(*Units), CP, *LIS->getSlotIndexes()))
       return true;
   return false;
 }

lib/CodeGen/RegisterCoalescer.h

@@ -63,6 +63,13 @@ namespace llvm {
       : TRI(tri), DstReg(0), SrcReg(0), DstIdx(0), SrcIdx(0),
         Partial(false), CrossClass(false), Flipped(false), NewRC(0) {}
 
+    /// Create a CoalescerPair representing a virtreg-to-physreg copy.
+    /// No need to call setRegisters().
+    CoalescerPair(unsigned VirtReg, unsigned PhysReg,
+                  const TargetRegisterInfo &tri)
+      : TRI(tri), DstReg(PhysReg), SrcReg(VirtReg), DstIdx(0), SrcIdx(0),
+        Partial(false), CrossClass(false), Flipped(false), NewRC(0) {}
+
     /// setRegisters - set registers to match the copy instruction MI. Return
     /// false if MI is not a coalescable copy instruction.
     bool setRegisters(const MachineInstr*);

test/CodeGen/PowerPC/2010-03-09-indirect-call.ll

@@ -9,9 +9,8 @@ target triple = "powerpc-apple-darwin11.0"
 
 define void @foo() nounwind ssp {
 entry:
-; Better: mtctr r12
-; CHECK: mr r12, [[REG:r[0-9]+]]
-; CHECK: mtctr [[REG]]
+; CHECK: mtctr r12
+; CHECK: bctrl
   %0 = load void (...)** @p, align 4              ; <void (...)*> [#uses=1]
   call void (...)* %0() nounwind
   br label %return

test/CodeGen/X86/phys_subreg_coalesce-3.ll

@@ -1,14 +1,10 @@
 ; RUN: llc < %s -mtriple=i386-apple-darwin | FileCheck %s
-; XFAIL: *
 ; rdar://5571034
 
 ; This requires physreg joining, %vreg13 is live everywhere:
 ; 304L		%CL<def> = COPY %vreg13:sub_8bit; GR32_ABCD:%vreg13
 ; 320L		%vreg15<def> = COPY %vreg19; GR32:%vreg15 GR32_NOSP:%vreg19
 ; 336L		%vreg15<def> = SAR32rCL %vreg15, %EFLAGS<imp-def,dead>, %CL<imp-use,kill>; GR32:%vreg15
-;
-; This test is XFAIL until the register allocator understands trivial physreg
-; interference. <rdar://9802098>
 
 define void @foo(i32* nocapture %quadrant, i32* nocapture %ptr, i32 %bbSize, i32 %bbStart, i32 %shifts) nounwind ssp {
 ; CHECK: foo:

test/CodeGen/X86/tls-pic.ll

@@ -76,12 +76,12 @@ entry:
 
 ; X32:    f5:
 ; X32:      leal {{[jk]}}@TLSLDM(%ebx)
-; X32-NEXT: calll ___tls_get_addr@PLT
-; X32-NEXT: movl {{[jk]}}@DTPOFF(%eax)
-; X32-NEXT: addl {{[jk]}}@DTPOFF(%eax)
+; X32: calll ___tls_get_addr@PLT
+; X32: movl {{[jk]}}@DTPOFF(%e
+; X32: addl {{[jk]}}@DTPOFF(%e
 
 ; X64:    f5:
 ; X64:      leaq {{[jk]}}@TLSLD(%rip), %rdi
-; X64-NEXT: callq	__tls_get_addr@PLT
-; X64-NEXT: movl {{[jk]}}@DTPOFF(%rax)
-; X64-NEXT: addl {{[jk]}}@DTPOFF(%rax)
+; X64: callq	__tls_get_addr@PLT
+; X64: movl {{[jk]}}@DTPOFF(%r
+; X64: addl {{[jk]}}@DTPOFF(%r