[llvm-commits] [llvm] r88672 - in /llvm/trunk: lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp test/CodeGen/X86/tailcall1.ll

[Dan Gohman]

Author: djg
Date: Fri Nov 13 12:49:38 2009
New Revision: 88672

URL: http://llvm.org/viewvc/llvm-project?rev=88672&view=rev
Log:
Don't let a noalias difference disrupt the tailcall optimization.

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=88672&r1=88671&r2=88672&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp Fri Nov 13 12:49:38 2009
@@ -4349,7 +4349,7 @@
 /// TargetLowering::IsEligibleForTailCallOptimization.
 ///
 static bool
-isInTailCallPosition(const Instruction *I, Attributes RetAttr,
+isInTailCallPosition(const Instruction *I, Attributes CalleeRetAttr,
                      const TargetLowering &TLI) {
   const BasicBlock *ExitBB = I->getParent();
   const TerminatorInst *Term = ExitBB->getTerminator();
@@ -4377,8 +4377,9 @@
   if (!Ret || Ret->getNumOperands() == 0) return true;
 
   // Conservatively require the attributes of the call to match those of
-  // the return.
-  if (F->getAttributes().getRetAttributes() != RetAttr)
+  // the return. Ignore noalias because it doesn't affect the call sequence.
+  unsigned CallerRetAttr = F->getAttributes().getRetAttributes();
+  if ((CalleeRetAttr ^ CallerRetAttr) & ~Attribute::NoAlias)
     return false;
 
   // Otherwise, make sure the unmodified return value of I is the return value.

Modified: llvm/trunk/test/CodeGen/X86/tailcall1.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/tailcall1.ll?rev=88672&r1=88671&r2=88672&view=diff

==============================================================================
--- llvm/trunk/test/CodeGen/X86/tailcall1.ll (original)
+++ llvm/trunk/test/CodeGen/X86/tailcall1.ll Fri Nov 13 12:49:38 2009
@@ -1,4 +1,4 @@
-; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL
+; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 3
 define fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32 %a4) {
 entry:
 	ret i32 %a3
@@ -9,3 +9,17 @@
 	%tmp11 = tail call fastcc i32 @tailcallee( i32 %in1, i32 %in2, i32 %in1, i32 %in2 )		; <i32> [#uses=1]
 	ret i32 %tmp11
 }
+
+declare fastcc i8* @alias_callee()
+
+define fastcc noalias i8* @noalias_caller() nounwind {
+  %p = tail call fastcc i8* @alias_callee()
+  ret i8* %p
+}
+
+declare fastcc noalias i8* @noalias_callee()
+
+define fastcc i8* @alias_caller() nounwind {
+  %p = tail call fastcc noalias i8* @noalias_callee()
+  ret i8* %p
+}