[opaque pointer type] Encode the pointee type in the bitcode for 'cmpxchg'

As a space optimization, this instruction would just encode the pointer
type of the first operand and use the knowledge that the second and
third operands would be of the pointee type of the first. When typed
pointers go away, this assumption will no longer be available - so
encode the type of the second operand explicitly and rely on that for
the third.

Test case added to demonstrate the backwards compatibility concern,
which only comes up when the definition of the second operand comes
after the use (hence the weird basic block sequence) - at which point
the type needs to be explicitly encoded in the bitcode and the record
length changes to accommodate this.

llvm-svn: 235966

5 files changed, 25 insertions, 7 deletions

diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
index 2db9d809c4f..fe6d3662954 100644
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -336,7 +336,7 @@ namespace bitc {
 
     FUNC_CODE_DEBUG_LOC        = 35, // DEBUG_LOC:  [Line,Col,ScopeVal, IAVal]
     FUNC_CODE_INST_FENCE       = 36, // FENCE: [ordering, synchscope]
-    FUNC_CODE_INST_CMPXCHG     = 37, // CMPXCHG: [ptrty,ptr,cmp,new, align, vol,
+    FUNC_CODE_INST_CMPXCHG_OLD = 37, // CMPXCHG: [ptrty,ptr,cmp,new, align, vol,
                                      //           ordering, synchscope]
     FUNC_CODE_INST_ATOMICRMW   = 38, // ATOMICRMW: [ptrty,ptr,val, operation,
                                      //             align, vol,
@@ -350,6 +350,8 @@ namespace bitc {
     FUNC_CODE_INST_GEP         = 43, // GEP:  [inbounds, n x operands]
     FUNC_CODE_INST_STORE       = 44, // STORE: [ptrty,ptr,valty,val, align, vol]
     FUNC_CODE_INST_STOREATOMIC = 45, // STORE: [ptrty,ptr,val, align, vol
+    FUNC_CODE_INST_CMPXCHG     = 46, // CMPXCHG: [ptrty,ptr,valty,cmp,new, align,
+                                     //           vol,ordering,synchscope]
   };
 
   enum UseListCodes {
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 1e9a8eb7fd1..cc554a91bea 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -4146,17 +4146,20 @@ std::error_code BitcodeReader::ParseFunctionBody(Function *F) {
       InstructionList.push_back(I);
       break;
     }
+    case bitc::FUNC_CODE_INST_CMPXCHG_OLD:
     case bitc::FUNC_CODE_INST_CMPXCHG: {
       // CMPXCHG:[ptrty, ptr, cmp, new, vol, successordering, synchscope,
       //          failureordering?, isweak?]
       unsigned OpNum = 0;
       Value *Ptr, *Cmp, *New;
       if (getValueTypePair(Record, OpNum, NextValueNo, Ptr) ||
-          popValue(Record, OpNum, NextValueNo,
-                    cast<PointerType>(Ptr->getType())->getElementType(), Cmp) ||
-          popValue(Record, OpNum, NextValueNo,
-                    cast<PointerType>(Ptr->getType())->getElementType(), New) ||
-          (Record.size() < OpNum + 3 || Record.size() > OpNum + 5))
+          (BitCode == bitc::FUNC_CODE_INST_CMPXCHG
+               ? getValueTypePair(Record, OpNum, NextValueNo, Cmp)
+               : popValue(Record, OpNum, NextValueNo,
+                          cast<PointerType>(Ptr->getType())->getElementType(),
+                          Cmp)) ||
+          popValue(Record, OpNum, NextValueNo, Cmp->getType(), New) ||
+          Record.size() < OpNum + 3 || Record.size() > OpNum + 5)
         return Error("Invalid record");
       AtomicOrdering SuccessOrdering = GetDecodedOrdering(Record[OpNum+1]);
       if (SuccessOrdering == NotAtomic || SuccessOrdering == Unordered)
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 840b75e496f..b6444b2d060 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -1917,7 +1917,7 @@ static void WriteInstruction(const Instruction &I, unsigned InstID,
   case Instruction::AtomicCmpXchg:
     Code = bitc::FUNC_CODE_INST_CMPXCHG;
     PushValueAndType(I.getOperand(0), InstID, Vals, VE);  // ptrty + ptr
-    pushValue(I.getOperand(1), InstID, Vals, VE);         // cmp.
+    PushValueAndType(I.getOperand(1), InstID, Vals, VE);         // cmp.
     pushValue(I.getOperand(2), InstID, Vals, VE);         // newval.
     Vals.push_back(cast<AtomicCmpXchgInst>(I).isVolatile());
     Vals.push_back(GetEncodedOrdering(
diff --git a/llvm/test/Bitcode/cmpxchg.3.6.ll b/llvm/test/Bitcode/cmpxchg.3.6.ll
new file mode 100644
index 00000000000..bec51a128c3
--- /dev/null
+++ b/llvm/test/Bitcode/cmpxchg.3.6.ll
@@ -0,0 +1,13 @@
+; RUN: llvm-dis < %s.bc | FileCheck %s
+
+define void @f2(i32* %x, i32 %y.orig, i32 %z) {
+entry:
+  br label %a
+b:
+  cmpxchg i32* %x, i32 %y, i32 %z acquire acquire
+; CHECK: cmpxchg i32* %x, i32 %y, i32 %z acquire acquire
+  ret void
+a:
+  %y = add i32 %y.orig, 1
+  br label %a
+}
diff --git a/llvm/test/Bitcode/cmpxchg.3.6.ll.bc b/llvm/test/Bitcode/cmpxchg.3.6.ll.bc
new file mode 100644
index 00000000000..1c66f934324
--- /dev/null
+++ b/llvm/test/Bitcode/cmpxchg.3.6.ll.bc