Use return value post-copy for inserting copies with source

from calls

Copy from original call value is incorrect because it is allocated on
unified return value and can be overwritten by subsequent calls, so we
should use post-copy instead

Author: skachkov-intel

IGC/VectorCompiler/lib/GenXCodeGen/GenXCoalescing.cpp

@@ -197,6 +197,7 @@ SPDX-License-Identifier: MIT
 #include "llvm/Support/Debug.h"
 
 #include <algorithm>
+#include <map>
 #include <vector>
 
 using namespace llvm;
@@ -317,6 +318,7 @@ namespace {
     std::vector<Candidate> NormalCandidates;
     std::vector<CallInst*> Callables;
     std::vector<CopyData> ToCopy;
+    std::map<SimpleValue, Value*> CallToRetVal;
     std::unordered_map<Instruction *, Value *> CopyCoalesced;
 
   public:
@@ -508,6 +510,7 @@ bool GenXCoalescing::runOnFunctionGroup(FunctionGroup &FG)
   CopyCandidates.clear();
   NormalCandidates.clear();
   Callables.clear();
+  CallToRetVal.clear();
   ToCopy.clear();
   CopyCoalesced.clear();
   return true;
@@ -1400,9 +1403,10 @@ void GenXCoalescing::processCalls(FunctionGroup *FG)
           showCoalesceFail(SimpleValue(CI, StructIdx), CI->getDebugLoc(),
                            "ret postcopy", DestLR, SourceLR);
           unsigned Num = Numbering->getRetPostCopyNumber(CI, StructIdx);
+          SimpleValue Source(CI, StructIdx);
           Instruction *NewCopy =
-              insertCopy(SimpleValue(CI, StructIdx), DestLR, InsertBefore,
-                         "retval.postcopy", Num);
+              insertCopy(Source, DestLR, InsertBefore, "retval.postcopy", Num);
+          CallToRetVal[Source] = NewCopy;
           IGC_ASSERT(NewCopy);
           if (AllUsesAreExtract) {
             // For a struct ret value where all the uses are non-struct
@@ -2039,6 +2043,9 @@ SortedCopies GenXCoalescing::getSortedCopyData() {
 Instruction *GenXCoalescing::createCopy(const CopyData &CD) {
   LiveRange *DestLR = Liveness->getLiveRange(CD.Dest);
   LiveRange *SourceLR = Liveness->getLiveRange(CD.Source);
+  SimpleValue Source = CD.Source;
+  if (auto It = CallToRetVal.find(Source); It != CallToRetVal.end())
+    Source = SimpleValue{It->second};
   Instruction *NewCopy = nullptr;
   switch (CD.CopyT) {
   case PHICOPY:
@@ -2052,7 +2059,7 @@ Instruction *GenXCoalescing::createCopy(const CopyData &CD) {
             : Numbering->getNumber(CD.InsertPoint);
     showCoalesceFail(CD.Dest, CD.InsertPoint->getDebugLoc(), "phi", DestLR,
                      SourceLR);
-    NewCopy = insertCopy(CD.Source, DestLR, CD.InsertPoint, "phicopy", Num);
+    NewCopy = insertCopy(Source, DestLR, CD.InsertPoint, "phicopy", Num);
     Phi->setIncomingValue(CD.UseInDest->getOperandNo(), NewCopy);
     break;
   }
@@ -2063,7 +2070,7 @@ Instruction *GenXCoalescing::createCopy(const CopyData &CD) {
     Instruction *DestInst = cast<Instruction>(CD.Dest.getValue());
     showCoalesceFail(CD.Dest, DestInst->getDebugLoc(), "two address", DestLR,
                      SourceLR);
-    NewCopy = insertCopy(CD.Source, DestLR, DestInst, "twoaddr",
+    NewCopy = insertCopy(Source, DestLR, DestInst, "twoaddr",
                          Numbering->getNumber(DestInst) - 1);
     NewCopy =
         insertIntoStruct(CD.Dest.getValue()->getType(), CD.Dest.getIndex(),