From: Brian Bohe <t-brboh@microsoft.com>
Date: Fri, 21 Feb 2020 19:43:36 +0000 (-0800)
Subject: Updating VariableLiveRange
X-Git-Tag: submit/tizen/20210909.063632~9481^2~3
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=93c209cb5d70de59637cc83e712b719fea51b520;p=platform%2Fupstream%2Fdotnet%2Fruntime.git

Updating VariableLiveRange

When a variable is being born at the same location it
died at the previous assembly instruction (in the same
group of instructions), we reported as it was alive
the whole time.
---

diff --git a/src/coreclr/src/jit/codegencommon.cpp b/src/coreclr/src/jit/codegencommon.cpp
index 1af9bc0..0bcd836 100644
--- a/src/coreclr/src/jit/codegencommon.cpp
+++ b/src/coreclr/src/jit/codegencommon.cpp
@@ -11466,10 +11466,21 @@ void CodeGenInterface::VariableLiveKeeper::VariableLiveDescriptor::startLiveRang
     // Is the first "VariableLiveRange" or the previous one has been closed so its "m_EndEmitLocation" is valid
     noway_assert(m_VariableLiveRanges->empty() || m_VariableLiveRanges->back().m_EndEmitLocation.Valid());
 
-    // Creates new live range with invalid end
-    m_VariableLiveRanges->emplace_back(varLocation, emitLocation(), emitLocation());
-    m_VariableLiveRanges->back().m_StartEmitLocation.CaptureLocation(emit);
-
+    if (!m_VariableLiveRanges->empty() &&
+        m_VariableLiveRanges->back().m_EndEmitLocation.IsPreviousIns(emit) &&
+        siVarLoc::Equals(&varLocation, &(m_VariableLiveRanges->back().m_VarLocation)))
+    {
+        // The variable is being born at the exactly same place just one assembly instructtion.
+        // We assume it never died.
+        m_VariableLiveRanges->back().m_EndEmitLocation.Init();
+    }
+    else
+    {
+        // Creates new live range with invalid end
+        m_VariableLiveRanges->emplace_back(varLocation, emitLocation(), emitLocation());
+        m_VariableLiveRanges->back().m_StartEmitLocation.CaptureLocation(emit);
+    }
+    
 #ifdef DEBUG
     if (!m_VariableLifeBarrier->hasLiveRangesToDump())
     {
diff --git a/src/coreclr/src/jit/emit.cpp b/src/coreclr/src/jit/emit.cpp
index 9288f6c..a95e70c 100644
--- a/src/coreclr/src/jit/emit.cpp
+++ b/src/coreclr/src/jit/emit.cpp
@@ -65,6 +65,15 @@ UNATIVE_OFFSET emitLocation::GetFuncletPrologOffset(emitter* emit) const
     return emit->emitCurIGsize;
 }
 
+// Returns true if the emitter is on the next instruction of the same group than this emitLocation
+bool emitLocation::IsPreviousIns(const emitter* emit) const
+{
+    assert(Valid());
+    bool sameGroup = ig == emit->emitCurIG;
+    bool sameInsNum = emitGetInsNumFromCodePos(codePos) == emitGetInsNumFromCodePos(emit->emitCurOffset()) - 1;
+    return sameGroup && sameInsNum;
+}
+
 #ifdef DEBUG
 void emitLocation::Print() const
 {
diff --git a/src/coreclr/src/jit/emit.h b/src/coreclr/src/jit/emit.h
index 37a1795..89d09e3 100644
--- a/src/coreclr/src/jit/emit.h
+++ b/src/coreclr/src/jit/emit.h
@@ -191,6 +191,8 @@ public:
 
     UNATIVE_OFFSET GetFuncletPrologOffset(emitter* emit) const;
 
+    bool emitLocation::IsPreviousIns(const emitter* emit) const;
+
 #ifdef DEBUG
     void Print() const;
 #endif // DEBUG
@@ -2389,7 +2391,7 @@ inline unsigned emitGetInsOfsFromCodePos(unsigned codePos)
     return (codePos >> 16);
 }
 
-inline unsigned emitter::emitCurOffset()
+inline unsigned emitter::emitCurOffset() const
 {
     unsigned codePos = emitCurIGinsCnt + (emitCurIGsize << 16);
 
diff --git a/src/coreclr/src/jit/emitpub.h b/src/coreclr/src/jit/emitpub.h
index cd28e03..bc8abf3 100644
--- a/src/coreclr/src/jit/emitpub.h
+++ b/src/coreclr/src/jit/emitpub.h
@@ -65,7 +65,7 @@ void emitFinishPrologEpilogGeneration();
 /************************************************************************/
 
 void*    emitCurBlock();
-unsigned emitCurOffset();
+unsigned emitCurOffset() const;
 
 UNATIVE_OFFSET emitCodeOffset(void* blockPtr, unsigned codeOffs);