Revert "Disable InstCombine unsafe folding bitcasts of calls w/ varargs."

This reverts commit d0e277d272.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149647 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -1105,12 +1105,21 @@ bool InstCombiner::transformConstExprCastCall(CallSite CS) {
     if (FT->isVarArg()!=cast<FunctionType>(APTy->getElementType())->isVarArg())
       return false;
   }
+      
+  if (FT->getNumParams() < NumActualArgs && FT->isVarArg() &&
+      !CallerPAL.isEmpty())
+    // In this case we have more arguments than the new function type, but we
+    // won't be dropping them.  Check that these extra arguments have attributes
+    // that are compatible with being a vararg call argument.
+    for (unsigned i = CallerPAL.getNumSlots(); i; --i) {
+      if (CallerPAL.getSlot(i - 1).Index <= FT->getNumParams())
+        break;
+      Attributes PAttrs = CallerPAL.getSlot(i - 1).Attrs;
+      if (PAttrs & Attribute::VarArgsIncompatible)
+        return false;
+    }
 
-  // If we're casting varargs to non-varargs, that may not be allowable
-  // under the ABI, so conservatively don't do anything.
-  if (FT->getNumParams() < NumActualArgs && FT->isVarArg())
-    return false;
-
+  
   // Okay, we decided that this is a safe thing to do: go ahead and start
   // inserting cast instructions as necessary.
   std::vector<Value*> Args;

test/Transforms/InstCombine/2008-01-06-BitCastAttributes.ll

@@ -0,0 +1,23 @@
+; Ignore stderr, we expect warnings there
+; RUN: opt < %s -instcombine 2> /dev/null -S | not grep bitcast
+
+define void @a() {
+	ret void
+}
+
+define signext i32 @b(i32* inreg  %x)   {
+	ret i32 0
+}
+
+define void @c(...) {
+	ret void
+}
+
+define void @g(i32* %y) {
+	call void bitcast (void ()* @a to void (i32*)*)( i32* noalias  %y )
+	call <2 x i32> bitcast (i32 (i32*)* @b to <2 x i32> (i32*)*)( i32* inreg  null )		; <<2 x i32>>:1 [#uses=0]
+	%x = call i64 bitcast (i32 (i32*)* @b to i64 (i32)*)( i32 0 )		; <i64> [#uses=0]
+	call void bitcast (void (...)* @c to void (i32)*)( i32 0 )
+	call void bitcast (void (...)* @c to void (i32)*)( i32 zeroext  0 )
+	ret void
+}

test/Transforms/InstCombine/call.ll

@@ -30,6 +30,20 @@ define i32 @test2(i32 %A) {
 }
 
 
+; Resolving this should insert a cast from sbyte to int, following the C 
+; promotion rules.
+define void @test3a(i8, ...) {unreachable }
+
+define void @test3(i8 %A, i8 %B) {
+        call void bitcast (void (i8, ...)* @test3a to void (i8, i8)*)( i8 %A, i8 %B 
+)
+        ret void
+; CHECK: %1 = zext i8 %B to i32
+; CHECK: call void (i8, ...)* @test3a(i8 %A, i32 %1)
+; CHECK: ret void
+}
+
+
 ; test conversion of return value...
 define i8 @test4a() {
         ret i8 0