[ICP] Do not attempt type matching for variable length arguments.

[twoh]

Summary

When performing indirect call promotion, current implementation inspects "all" parameters of the callsite and attemps to match with the formal argument type of the callee function. However, it is not possible to find the type for variable length arguments, and the compiler crashes when it attemps to match the type for variable lenght argument.

It seems that the bug is introduced with D40658. Prior to that, the type matching is performed only for the parameters whose ID is less than callee->getFunctionNumParams(). The attached test case will crash without the patch.

[mssimpso]

Thanks for catching this bug! Yep, it was introduced with the refactoring done in D40658. I just have one minor comment.

lib/Transforms/Utils/CallPromotionUtils.cpp

394 ↗

(On Diff #143796)

It's probably more straightforward to rewrite the loop like what's below, instead of adding the check inside the loop.

for (unsigned ArgNo = 0; ArgNo < CalleeParamNum; ++ArgNo) {
  ...
}

[twoh]

Addressing comment from @mssimpso. Thanks!

[mssimpso]

LGTM.

llvm/trunk/lib/Transforms/Utils/CallPromotionUtils.cpp

Instruction *llvm::promoteCall(CallSite CS, Function *Callee,
   Type *CalleeRetTy = Callee->getReturnType();
 
   // Change the function type of the call site the match that of the callee.
   CS.mutateFunctionType(Callee->getFunctionType());
 
   // Inspect the arguments of the call site. If an argument's type doesn't
   // match the corresponding formal argument's type in the callee, bitcast it
   // to the correct type.
-  for (Use &U : CS.args()) {
-    unsigned ArgNo = CS.getArgumentNo(&U);
-    Type *FormalTy = Callee->getFunctionType()->getParamType(ArgNo);
-    Type *ActualTy = U.get()->getType();
+  auto CalleeType = Callee->getFunctionType();
+  auto CalleeParamNum = CalleeType->getNumParams();
+  for (unsigned ArgNo = 0; ArgNo < CalleeParamNum; ++ArgNo) {
+    auto *Arg = CS.getArgument(ArgNo); 
+    Type *FormalTy = CalleeType->getParamType(ArgNo);
+    Type *ActualTy = Arg->getType();
     if (FormalTy != ActualTy) {
-      auto *Cast = CastInst::Create(Instruction::BitCast, U.get(), FormalTy, "",
+      auto *Cast = CastInst::Create(Instruction::BitCast, Arg, FormalTy, "",
                                     CS.getInstruction());
       CS.setArgument(ArgNo, Cast);
     }
   }
 
   // If the return type of the call site doesn't match that of the callee, cast
   // the returned value to the appropriate type.
   if (!CallSiteRetTy->isVoidTy() && CallSiteRetTy != CalleeRetTy)

llvm/trunk/test/Transforms/PGOProfile/indirect_call_promotion_vla.ll

+; RUN: opt < %s -pgo-icall-prom -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.A = type { i8 }
+%struct.B = type { i8 }
+@foo = common global i32 (%struct.A*, ...)* null, align 8
+
+define i32 @func1(%struct.B* %x, ...) {
+entry:
+  ret i32 0
+}
+
+define i32 @bar(%struct.A* %x) {
+entry:
+  %tmp = load i32 (%struct.A*, ...)*, i32 (%struct.A*, ...)** @foo, align 8
+; CHECK:   [[CMP:%[0-9]+]] = icmp eq i32 (%struct.A*, ...)* %tmp, bitcast (i32 (%struct.B*, ...)* @func1 to i32 (%struct.A*, ...)*)
+; CHECK:   br i1 [[CMP]], label %if.true.direct_targ, label %if.false.orig_indirect, !prof [[BRANCH_WEIGHT:![0-9]+]]
+; CHECK: if.true.direct_targ:
+; CHECK:   [[DIRCALL_RET:%[0-9]+]] = call i32 (%struct.B*, ...) @func1
+; CHECK:   br label %if.end.icp
+  %call = call i32 (%struct.A*, ...) %tmp(%struct.A* %x, i32 0), !prof !1
+  ret i32 %call
+}
+
+; CHECK: [[BRANCH_WEIGHT]] = !{!"branch_weights", i32 1500, i32 100}
+!1 = !{!"VP", i32 0, i64 1600, i64 -2545542355363006406, i64 1500}