[llvm-commits] [llvm] r136722 - in /llvm/trunk: lib/Transforms/Utils/Local.cpp test/Transforms/InstCombine/deadcode.ll

[Nick Lewycky]

Author: nicholas
Date: Tue Aug  2 16:19:27 2011
New Revision: 136722

URL: http://llvm.org/viewvc/llvm-project?rev=136722&view=rev
Log:
Lifetime intrinsics on undef are dead.

Modified:
    llvm/trunk/lib/Transforms/Utils/Local.cpp
    llvm/trunk/test/Transforms/InstCombine/deadcode.ll

Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=136722&r1=136721&r2=136722&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/Local.cpp Tue Aug  2 16:19:27 2011
@@ -229,10 +229,10 @@
   // We don't want debug info removed by anything this general, unless
   // debug info is empty.
   if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
-    if (DDI->getAddress()) 
+    if (DDI->getAddress())
       return false;
     return true;
-  } 
+  }
   if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
     if (DVI->getValue())
       return false;
@@ -243,10 +243,16 @@
 
   // Special case intrinsics that "may have side effects" but can be deleted
   // when dead.
-  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
     // Safe to delete llvm.stacksave if dead.
     if (II->getIntrinsicID() == Intrinsic::stacksave)
       return true;
+
+    // Lifetime intrinsics are dead when their right-hand is undef.
+    if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+        II->getIntrinsicID() == Intrinsic::lifetime_end)
+      return isa<UndefValue>(II->getArgOperand(1));
+  }
   return false;
 }
 

Modified: llvm/trunk/test/Transforms/InstCombine/deadcode.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/deadcode.ll?rev=136722&r1=136721&r2=136722&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/deadcode.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/deadcode.ll Tue Aug  2 16:19:27 2011
@@ -1,5 +1,5 @@
 ; RUN: opt < %s -instcombine -S | grep {ret i32 %A}
-; RUN: opt < %s -die -S | not grep call.*llvm.stacksave
+; RUN: opt < %s -die -S | not grep call.*llvm
 
 define i32 @test(i32 %A) {
 	%X = or i1 false, false		
@@ -22,3 +22,12 @@
 
 declare i8* @llvm.stacksave()
 
+declare void @llvm.lifetime.start(i64, i8*)
+declare void @llvm.lifetime.end(i64, i8*)
+
+define void @test3() {
+  call void @llvm.lifetime.start(i64 -1, i8* undef)
+  call void @llvm.lifetime.end(i64 -1, i8* undef)
+  ret void
+}
+