Eliminate trivial redundant loads across nocapture+readonly calls to uncaptured

[oota-llvm.git] / lib / Analysis / AliasAnalysis.cpp

diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 210b80ab63ef7b2a1f5b89d79ac6d1e38ea841b2..054930c0e1936c2ec64450dd89defbe6990b34e9 100644 (file)
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -450,6 +450,7 @@ AliasAnalysis::callCapturesBefore(const Instruction *I,
     return AliasAnalysis::ModRef;
 
   unsigned ArgNo = 0;
+  AliasAnalysis::ModRefResult R = AliasAnalysis::NoModRef;
   for (ImmutableCallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
        CI != CE; ++CI, ++ArgNo) {
     // Only look at the no-capture or byval pointer arguments.  If this
@@ -463,12 +464,18 @@ AliasAnalysis::callCapturesBefore(const Instruction *I,
     // is impossible to alias the pointer we're checking.  If not, we have to
     // assume that the call could touch the pointer, even though it doesn't
     // escape.
-    if (!isNoAlias(AliasAnalysis::Location(*CI),
-                   AliasAnalysis::Location(Object))) {
-      return AliasAnalysis::ModRef;
+    if (isNoAlias(AliasAnalysis::Location(*CI),
+                 AliasAnalysis::Location(Object)))
+      continue;
+    if (CS.doesNotAccessMemory(ArgNo))
+      continue;
+    if (CS.onlyReadsMemory(ArgNo)) {
+      R = AliasAnalysis::Ref;
+      continue;
     }
+    return AliasAnalysis::ModRef;
   }
-  return AliasAnalysis::NoModRef;
+  return R;
 }
 
 // AliasAnalysis destructor: DO NOT move this to the header file for
@@ -537,6 +544,15 @@ bool llvm::isNoAliasCall(const Value *V) {
   return false;
 }
 
+/// isNoAliasArgument - Return true if this is an argument with the noalias
+/// attribute.
+bool llvm::isNoAliasArgument(const Value *V)
+{
+  if (const Argument *A = dyn_cast<Argument>(V))
+    return A->hasNoAliasAttr();
+  return false;
+}
+
 /// isIdentifiedObject - Return true if this pointer refers to a distinct and
 /// identifiable object.  This returns true for:
 ///    Global Variables and Functions (but not Global Aliases)