[llvm-commits] [llvm] r61040 - in /llvm/trunk: lib/Analysis/BasicAliasAnalysis.cpp test/Analysis/BasicAA/nocapture.ll

[Chris Lattner]

Author: lattner
Date: Mon Dec 15 12:59:22 2008
New Revision: 61040

URL: http://llvm.org/viewvc/llvm-project?rev=61040&view=rev
Log:
Teach basicaa to use the nocapture attribute when possible.  When the
intrinsics are properly marked nocapture, the fixme should be addressed.


Added:
    llvm/trunk/test/Analysis/BasicAA/nocapture.ll
Modified:
    llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=61040&r1=61039&r2=61040&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Mon Dec 15 12:59:22 2008
@@ -63,12 +63,23 @@
       // callees could modify it.
       break; // next use
     case Instruction::Call:
-      // If the call is to a few known safe intrinsics, we know that it does
-      // not escape.
-      // TODO: Eventually just check the 'nocapture' attribute.
-      if (!isa<MemIntrinsic>(I))
-        return true;
-      break;  // next use
+      // If the argument to the call has the nocapture attribute, then the call
+      // may store or load to the pointer, but it cannot escape.
+      if (cast<CallInst>(I)->paramHasAttr(UI.getOperandNo(), 
+                                          Attribute::NoCapture))
+        continue;
+
+      // FIXME: MemIntrinsics should have their operands marked nocapture!
+      if (isa<MemIntrinsic>(I))
+        continue;  // next use
+      return true;
+    case Instruction::Invoke:
+      // If the argument to the call has the nocapture attribute, then the call
+      // may store or load to the pointer, but it cannot escape.
+      if (cast<InvokeInst>(I)->paramHasAttr(UI.getOperandNo()-2,
+                                            Attribute::NoCapture))
+        continue;
+      return true;
     default:
       return true;
     }

Added: llvm/trunk/test/Analysis/BasicAA/nocapture.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/nocapture.ll?rev=61040&view=auto

==============================================================================
--- llvm/trunk/test/Analysis/BasicAA/nocapture.ll (added)
+++ llvm/trunk/test/Analysis/BasicAA/nocapture.ll Mon Dec 15 12:59:22 2008
@@ -0,0 +1,13 @@
+; RUN: llvm-as < %s | opt -basicaa -gvn -instcombine | llvm-dis | grep {ret i32 0}
+
+declare i32* @test(i32* nocapture)
+
+define i32 @test2() {
+	%P = alloca i32
+	%Q = call i32* @test(i32* %P)
+	%a = load i32* %P
+	store i32 4, i32* %Q   ;; cannot clobber P since it is nocapture.
+	%b = load i32* %P
+	%c = sub i32 %a, %b
+	ret i32 %c
+}