[llvm] r226708 - InstCombine: Don't strip bitcasts off of callsites marked 'thunk'

[David Majnemer]

Author: majnemer
Date: Wed Jan 21 16:32:04 2015
New Revision: 226708

URL: http://llvm.org/viewvc/llvm-project?rev=226708&view=rev
Log:
InstCombine: Don't strip bitcasts off of callsites marked 'thunk'

The return type of a thunk is meaningless, we just want the arguments
and return value to be forwarded.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/trunk/test/Transforms/InstCombine/call-cast-target.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=226708&r1=226707&r2=226708&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Wed Jan 21 16:32:04 2015
@@ -1381,6 +1381,10 @@ bool InstCombiner::transformConstExprCas
     dyn_cast<Function>(CS.getCalledValue()->stripPointerCasts());
   if (!Callee)
     return false;
+  // The prototype of thunks are a lie, don't try to directly call such
+  // functions.
+  if (Callee->hasFnAttribute("thunk"))
+    return false;
   Instruction *Caller = CS.getInstruction();
   const AttributeSet &CallerPAL = CS.getAttributes();
 

Modified: llvm/trunk/test/Transforms/InstCombine/call-cast-target.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/call-cast-target.ll?rev=226708&r1=226707&r2=226708&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/call-cast-target.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/call-cast-target.ll Wed Jan 21 16:32:04 2015
@@ -61,3 +61,14 @@ entry:
   %call = tail call i32 bitcast (i32 (i64)* @fn3 to i32 (i32*)*)(i32* %a)
   ret i32 %call
 }
+
+declare i32 @fn4(i32) "thunk"
+
+define i32 @test4(i32* %a) {
+; CHECK-LABEL: @test4
+; CHECK:      %[[call:.*]] = tail call i32 bitcast (i32 (i32)* @fn4 to i32 (i32*)*)(i32* %a)
+; CHECK-NEXT: ret i32 %[[call]]
+entry:
+  %call = tail call i32 bitcast (i32 (i32)* @fn4 to i32 (i32*)*)(i32* %a)
+  ret i32 %call
+}