From: Duncan Sands <baldrick@free.fr>
Date: Thu, 22 Nov 2007 21:43:27 +0000 (+0000)
Subject: Teach alias analysis about readnone/readonly functions.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=920653d41e101787cad4b733ae5c3d4241aa0cec;p=oota-llvm.git

Teach alias analysis about readnone/readonly functions.
Based on a patch by Török Edwin.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44279 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index cbbc530fefb..c6e34da5ac3 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -952,6 +952,12 @@ BasicAliasAnalysis::getModRefBehavior(Function *F, CallSite CS,
   if (Ptr != OnlyReadsMemoryTable->end() && strcmp(*Ptr, NamePtr) == 0)
     return OnlyReadsMemory;
 
+  const ParamAttrsList *Attrs = F->getFunctionType()->getParamAttrs();
+  if (Attrs && Attrs->paramHasAttr(0, ParamAttr::ReadNone))
+    return DoesNotAccessMemory;
+  if (Attrs && Attrs->paramHasAttr(0, ParamAttr::ReadOnly))
+    return OnlyReadsMemory;
+
   return UnknownModRefBehavior;
 }
 
diff --git a/test/Analysis/BasicAA/pure-const-dce.ll b/test/Analysis/BasicAA/pure-const-dce.ll
new file mode 100644
index 00000000000..6abc7da30e4
--- /dev/null
+++ b/test/Analysis/BasicAA/pure-const-dce.ll
@@ -0,0 +1,33 @@
+; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestConst | count 2
+; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestPure  | not count 2
+; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestNone  | count 4
+@g = global i32 0		; <i32*> [#uses=1]
+
+define i32 @test() {
+entry:
+	%tmp0 = call i32 @TestConst( i32 5 ) readnone 		; <i32> [#uses=1]
+	%tmp1 = call i32 @TestPure( i32 6 ) readonly 		; <i32> [#uses=1]
+	%tmp2 = call i32 @TestNone( i32 7 )		; <i32> [#uses=1]
+	store i32 1, i32* @g
+	%tmp3 = call i32 @TestConst( i32 5 ) readnone 		; <i32> [#uses=1]
+	%tmp4 = call i32 @TestConst( i32 5 ) readnone 		; <i32> [#uses=1]
+	%tmp5 = call i32 @TestPure( i32 6 ) readonly 		; <i32> [#uses=1]
+	%tmp6 = call i32 @TestPure( i32 6 ) readonly 		; <i32> [#uses=1]
+	%tmp7 = call i32 @TestNone( i32 7 )		; <i32> [#uses=1]
+	%tmp8 = call i32 @TestNone( i32 7 )		; <i32> [#uses=1]
+	%sum0 = add i32 %tmp0, %tmp1		; <i32> [#uses=1]
+	%sum1 = add i32 %sum0, %tmp2		; <i32> [#uses=1]
+	%sum2 = add i32 %sum1, %tmp3		; <i32> [#uses=1]
+	%sum3 = add i32 %sum2, %tmp4		; <i32> [#uses=1]
+	%sum4 = add i32 %sum3, %tmp5		; <i32> [#uses=1]
+	%sum5 = add i32 %sum4, %tmp6		; <i32> [#uses=1]
+	%sum6 = add i32 %sum5, %tmp7		; <i32> [#uses=1]
+	%sum7 = add i32 %sum6, %tmp8		; <i32> [#uses=1]
+	ret i32 %sum7
+}
+
+declare i32 @TestConst(i32) readnone
+
+declare i32 @TestPure(i32) readonly
+
+declare i32 @TestNone(i32)