Verify a couple more fields in STATEPOINT instructions

While doing so, clarify the comments and update them to reflect current reality.

Note: I'm going to let this sit for a week or so before adding further verification.  I want to give this time to cycle through bots and merge it into our downstream tree before pushing this further.
llvm-svn: 304565

llvm/include/llvm/CodeGen/StackMaps.h

@@ -145,11 +145,18 @@ public:
 ///
 /// Statepoint operands take the form:
 ///   <id>, <num patch bytes >, <num call arguments>, <call target>,
-///   [call arguments], <StackMaps::ConstantOp>, <calling convention>,
+///   [call arguments...],
+///   <StackMaps::ConstantOp>, <calling convention>,
 ///   <StackMaps::ConstantOp>, <statepoint flags>,
-///   <StackMaps::ConstantOp>, <num other args>, [other args],
-///   [gc values]
+///   <StackMaps::ConstantOp>, <num deopt args>, [deopt args...],
+///   <gc base/derived pairs...> <gc allocas...>
+/// Note that the last two sets of arguments are not currently length
+///   prefixed.
 class StatepointOpers {
+  // TODO:: we should change the STATEPOINT representation so that CC and
+  // Flags should be part of meta operands, with args and deopt operands, and
+  // gc operands all prefixed by their length and a type code. This would be
+  // much more consistent. 
 public:
   // These values are aboolute offsets into the operands of the statepoint
   // instruction.
@@ -157,7 +164,7 @@ public:
 
   // These values are relative offests from the start of the statepoint meta
   // arguments (i.e. the end of the call arguments).
-  enum { CCOffset = 1, FlagsOffset = 3, NumVMSArgsOffset = 5 };
+  enum { CCOffset = 1, FlagsOffset = 3, NumDeoptOperandsOffset = 5 };
 
   explicit StatepointOpers(const MachineInstr *MI) : MI(MI) {}
 

llvm/lib/CodeGen/MachineVerifier.cpp

@@ -932,6 +932,20 @@ void MachineVerifier::visitMachineInstrBefore(const MachineInstr *MI) {
         !MI->getOperand(StatepointOpers::NCallArgsPos).isImm())
       report("meta operands to STATEPOINT not constant!", MI);
     break;
+
+    auto VerifyStackMapConstant = [&](unsigned Offset) {
+      if (!MI->getOperand(Offset).isImm() ||
+          MI->getOperand(Offset).getImm() != StackMaps::ConstantOp || 
+          !MI->getOperand(Offset + 1).isImm()) 
+        report("stack map constant to STATEPOINT not well formed!", MI);
+    };
+    const unsigned VarStart = StatepointOpers(MI).getVarIdx();
+    VerifyStackMapConstant(VarStart + StatepointOpers::CCOffset);
+    VerifyStackMapConstant(VarStart + StatepointOpers::FlagsOffset);
+    VerifyStackMapConstant(VarStart + StatepointOpers::NumDeoptOperandsOffset);
+
+    // TODO: verify we have properly encoded deopt arguments
+   
   };
 }