From d0e277d272d517ca1cda368267d199f0da7cad95 Mon Sep 17 00:00:00 2001
From: Jim Grosbach <grosbach@apple.com>
Date: Wed, 1 Feb 2012 00:08:17 +0000
Subject: [PATCH] Disable InstCombine unsafe folding bitcasts of calls w/
 varargs.

Changing arguments from being passed as fixed to varargs is unsafe, as
the ABI may require they be handled differently (stack vs. register, for
example).

Remove two tests which rely on the bitcast being folded into the direct
call, which is exactly the transformation that's unsafe.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149457 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstCombineCalls.cpp          | 19 ++++-----------
 .../2008-01-06-BitCastAttributes.ll           | 23 -------------------
 test/Transforms/InstCombine/call.ll           | 14 -----------
 3 files changed, 5 insertions(+), 51 deletions(-)
 delete mode 100644 test/Transforms/InstCombine/2008-01-06-BitCastAttributes.ll

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index a87fbbd9895..c3c13ae362f 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1105,21 +1105,12 @@ 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;
diff --git a/test/Transforms/InstCombine/2008-01-06-BitCastAttributes.ll b/test/Transforms/InstCombine/2008-01-06-BitCastAttributes.ll
deleted file mode 100644
index 23b606779e6..00000000000
--- a/test/Transforms/InstCombine/2008-01-06-BitCastAttributes.ll
+++ /dev/null
@@ -1,23 +0,0 @@
-; 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
-}
diff --git a/test/Transforms/InstCombine/call.ll b/test/Transforms/InstCombine/call.ll
index 96ec420eaa8..ca36484bc25 100644
--- a/test/Transforms/InstCombine/call.ll
+++ b/test/Transforms/InstCombine/call.ll
@@ -30,20 +30,6 @@ 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
-- 
2.34.1