From: Hans Wennborg <hans@hanshq.net>
Date: Thu, 22 Jan 2015 19:40:47 +0000 (+0000)
Subject: Merging r226708:
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4f7a137d6124f56313b4359d9c584651523d7236;p=llvm

Merging r226708:
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r226708 | majnemer | 2015-01-21 14:32:04 -0800 (Wed, 21 Jan 2015) | 4 lines

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.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_36@226854 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstCombineCalls.cpp b/lib/Transforms/InstCombine/InstCombineCalls.cpp
index dab2c4b47ad..83b4b82311f 100644
--- a/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1376,6 +1376,10 @@ bool InstCombiner::transformConstExprCastCall(CallSite CS) {
     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();
 
diff --git a/test/Transforms/InstCombine/call-cast-target.ll b/test/Transforms/InstCombine/call-cast-target.ll
index b82dd99db36..4a5c94961e2 100644
--- a/test/Transforms/InstCombine/call-cast-target.ll
+++ b/test/Transforms/InstCombine/call-cast-target.ll
@@ -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
+}