Simplify test for sret attribute in instcombine

This change is correct because the verifier requires that at most one
argument be marked 'sret'.

NFC, removes a use of AttributeList slot APIs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300784 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -4068,21 +4068,15 @@ bool InstCombiner::transformConstExprCastCall(CallSite CS) {
   }
 
   if (FT->getNumParams() < NumActualArgs && FT->isVarArg() &&
-      !CallerPAL.isEmpty())
+      !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) {
-      unsigned Index = CallerPAL.getSlotIndex(i - 1);
-      if (Index <= FT->getNumParams())
-        break;
-
-      // Check if it has an attribute that's incompatible with varargs.
-      AttributeList PAttrs = CallerPAL.getSlotAttributes(i - 1);
-      if (PAttrs.hasAttribute(Index, Attribute::StructRet))
-        return false;
-    }
-
+    unsigned SRetIdx;
+    if (CallerPAL.hasAttrSomewhere(Attribute::StructRet, &SRetIdx) &&
+        SRetIdx > FT->getNumParams())
+      return false;
+  }
 
   // Okay, we decided that this is a safe thing to do: go ahead and start
   // inserting cast instructions as necessary.

test/Transforms/InstCombine/call-cast-attrs.ll

@@ -0,0 +1,29 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+define signext i32 @b(i32* inreg %x)   {
+  ret i32 0
+}
+
+define void @c(...) {
+  ret void
+}
+
+declare void @useit(i32)
+
+define void @d(i32 %x, ...) {
+  call void @useit(i32 %x)
+  ret void
+}
+
+define void @g(i32* %y) {
+  call i32 bitcast (i32 (i32*)* @b to i32 (i32)*)(i32 zeroext 0)
+  call void bitcast (void (...)* @c to void (i32*)*)(i32* %y)
+  call void bitcast (void (...)* @c to void (i32*)*)(i32* sret %y)
+  call void bitcast (void (i32, ...)* @d to void (i32, i32*)*)(i32 0, i32* sret %y)
+  ret void
+}
+; CHECK-LABEL: define void @g(i32* %y)
+; CHECK: call i32 bitcast (i32 (i32*)* @b to i32 (i32)*)(i32 zeroext 0)
+; CHECK: call void (...) @c(i32* %y)
+; CHECK: call void bitcast (void (...)* @c to void (i32*)*)(i32* sret %y)
+; CHECK: call void bitcast (void (i32, ...)* @d to void (i32, i32*)*)(i32 0, i32* sret %y)