[llvm-commits] [llvm] r88737 - in /llvm/trunk: lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp test/CodeGen/X86/tailcall1.ll

[Dan Gohman]

Author: djg
Date: Fri Nov 13 20:06:30 2009
New Revision: 88737

URL: http://llvm.org/viewvc/llvm-project?rev=88737&view=rev
Log:
Enable the tail call optimization when the caller returns undef.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
    llvm/trunk/test/CodeGen/X86/tailcall1.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp?rev=88737&r1=88736&r2=88737&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp Fri Nov 13 20:06:30 2009
@@ -4376,6 +4376,10 @@
   // what the call's return type is.
   if (!Ret || Ret->getNumOperands() == 0) return true;
 
+  // If the return value is undef, it doesn't matter what the call's
+  // return type is.
+  if (isa<UndefValue>(Ret->getOperand(0))) return true;
+
   // Conservatively require the attributes of the call to match those of
   // the return. Ignore noalias because it doesn't affect the call sequence.
   unsigned CallerRetAttr = F->getAttributes().getRetAttributes();

Modified: llvm/trunk/test/CodeGen/X86/tailcall1.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tailcall1.ll?rev=88737&r1=88736&r2=88737&view=diff

==============================================================================
--- llvm/trunk/test/CodeGen/X86/tailcall1.ll (original)
+++ llvm/trunk/test/CodeGen/X86/tailcall1.ll Fri Nov 13 20:06:30 2009
@@ -1,4 +1,4 @@
-; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 3
+; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 4
 define fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32 %a4) {
 entry:
 	ret i32 %a3
@@ -23,3 +23,10 @@
   %p = tail call fastcc noalias i8* @noalias_callee()
   ret i8* %p
 }
+
+declare fastcc i32 @i32_callee()
+
+define fastcc i32 @ret_undef() nounwind {
+  %p = tail call fastcc i32 @i32_callee()
+  ret i32 undef
+}