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 cbbc530fefb54f60be8bb3ff939c3254e6721452..c6e34da5ac3259d97181ceaded824eeb2134e287 100644 (file)
--- 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 (file)
index 0000000..6abc7da
--- /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)