From 79b0c3f0b9d91bbda354a2c6f22b6578655a5143 Mon Sep 17 00:00:00 2001
From: Alkis Evlogimenos <alkis@evlogimenos.com>
Date: Fri, 23 Jan 2004 13:37:51 +0000
Subject: [PATCH] Fix failing test cases with joined live intervals. It turns
 out that when joining we need to check if we overlap with the second interval
 or any of its aliases.

Also make joining intervals the default.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10973 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/LiveIntervalAnalysis.h |  2 ++
 include/llvm/CodeGen/LiveIntervals.h        |  2 ++
 lib/CodeGen/LiveIntervalAnalysis.cpp        | 27 ++++++++++++++++++---
 lib/CodeGen/LiveIntervalAnalysis.h          |  2 ++
 4 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index 292c5111209..7cf627b3558 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -162,6 +162,8 @@ namespace llvm {
                                        MachineBasicBlock::iterator mi,
                                        unsigned reg);
 
+        bool overlapsAliases(const Interval& lhs, const Interval& rhs) const;
+
         unsigned getInstructionIndex(MachineInstr* instr) const;
 
         void printRegName(unsigned reg) const;
diff --git a/include/llvm/CodeGen/LiveIntervals.h b/include/llvm/CodeGen/LiveIntervals.h
index 292c5111209..7cf627b3558 100644
--- a/include/llvm/CodeGen/LiveIntervals.h
+++ b/include/llvm/CodeGen/LiveIntervals.h
@@ -162,6 +162,8 @@ namespace llvm {
                                        MachineBasicBlock::iterator mi,
                                        unsigned reg);
 
+        bool overlapsAliases(const Interval& lhs, const Interval& rhs) const;
+
         unsigned getInstructionIndex(MachineInstr* instr) const;
 
         void printRegName(unsigned reg) const;
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index fb11ff093bb..75fcfd09ea9 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -49,7 +49,7 @@ namespace {
     cl::opt<bool>
     join("join-liveintervals",
          cl::desc("Join compatible live intervals"),
-         cl::init(false));
+         cl::init(true));
 };
 
 void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const
@@ -387,26 +387,31 @@ void LiveIntervals::joinIntervals()
                 Intervals::iterator srcInt = r2iSrc->second;
                 Intervals::iterator dstInt = r2iDst->second;
 
+                // src is a physical register
                 if (srcInt->reg < MRegisterInfo::FirstVirtualRegister) {
                     if (dstInt->reg == srcInt->reg ||
                         (dstInt->reg >= MRegisterInfo::FirstVirtualRegister &&
-                         !dstInt->overlaps(*srcInt))) {
+                         !srcInt->overlaps(*dstInt) &&
+                         !overlapsAliases(*srcInt, *dstInt))) {
                         srcInt->join(*dstInt);
                         r2iDst->second = r2iSrc->second;
                         r2rMap_.insert(std::make_pair(dstInt->reg, srcInt->reg));
                         intervals_.erase(dstInt);
                     }
                 }
+                // dst is a physical register
                 else if (dstInt->reg < MRegisterInfo::FirstVirtualRegister) {
                     if (srcInt->reg == dstInt->reg ||
                         (srcInt->reg >= MRegisterInfo::FirstVirtualRegister &&
-                         !srcInt->overlaps(*dstInt))) {
+                         !dstInt->overlaps(*srcInt) &&
+                         !overlapsAliases(*dstInt, *srcInt))) {
                         dstInt->join(*srcInt);
                         r2iSrc->second = r2iDst->second;
                         r2rMap_.insert(std::make_pair(srcInt->reg, dstInt->reg));
                         intervals_.erase(srcInt);
                     }
                 }
+                // neither src nor dst are physical registers
                 else {
                     const TargetRegisterClass *srcRc, *dstRc;
                     srcRc = mf_->getSSARegMap()->getRegClass(srcInt->reg);
@@ -432,6 +437,22 @@ void LiveIntervals::joinIntervals()
                
 }
 
+bool LiveIntervals::overlapsAliases(const Interval& lhs,
+                                    const Interval& rhs) const
+{
+    assert(lhs.reg < MRegisterInfo::FirstVirtualRegister &&
+           "first interval must describe a physical register");
+
+    for (const unsigned* as = mri_->getAliasSet(lhs.reg); *as; ++as) {
+        Reg2IntervalMap::const_iterator r2i = r2iMap_.find(*as);
+        assert(r2i != r2iMap_.end() && "alias does not have interval?");
+        if (rhs.overlaps(*r2i->second))
+            return true;
+    }
+
+    return false;
+}
+
 LiveIntervals::Interval::Interval(unsigned r)
     : reg(r),
       weight((r < MRegisterInfo::FirstVirtualRegister ?
diff --git a/lib/CodeGen/LiveIntervalAnalysis.h b/lib/CodeGen/LiveIntervalAnalysis.h
index 292c5111209..7cf627b3558 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.h
+++ b/lib/CodeGen/LiveIntervalAnalysis.h
@@ -162,6 +162,8 @@ namespace llvm {
                                        MachineBasicBlock::iterator mi,
                                        unsigned reg);
 
+        bool overlapsAliases(const Interval& lhs, const Interval& rhs) const;
+
         unsigned getInstructionIndex(MachineInstr* instr) const;
 
         void printRegName(unsigned reg) const;