Revert a bit of r137667; the logic in question can safely handle atomic load/store.

llvm-svn: 137702

2 files changed, 25 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index c43f4b9870a..0edf3427507 100644
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -163,15 +163,15 @@ bool FunctionAttrs::AddReadAttrs(const CallGraphSCC &SCC) {
           ReadsMemory = true;
         continue;
       } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
-        // Ignore non-volatile loads from local memory.
-        if (LI->isUnordered()) {
+        // Ignore non-volatile loads from local memory. (Atomic is okay here.)
+        if (!LI->isVolatile()) {
           AliasAnalysis::Location Loc = AA->getLocation(LI);
           if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
             continue;
         }
       } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
-        // Ignore non-volatile stores to local memory.
-        if (SI->isUnordered()) {
+        // Ignore non-volatile stores to local memory. (Atomic is okay here.)
+        if (!SI->isVolatile()) {
           AliasAnalysis::Location Loc = AA->getLocation(SI);
           if (AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
             continue;
diff --git a/llvm/test/Transforms/FunctionAttrs/atomic.ll b/llvm/test/Transforms/FunctionAttrs/atomic.ll
new file mode 100644
index 00000000000..62f8fa5a1df
--- /dev/null
+++ b/llvm/test/Transforms/FunctionAttrs/atomic.ll
@@ -0,0 +1,21 @@
+; RUN: opt -basicaa -functionattrs -S < %s | FileCheck %s
+
+; Atomic load/store to local doesn't affect whether a function is
+; readnone/readonly.
+define i32 @test1(i32 %x) uwtable ssp {
+; CHECK: define i32 @test1(i32 %x) uwtable readnone ssp {
+entry:
+  %x.addr = alloca i32, align 4
+  store atomic i32 %x, i32* %x.addr seq_cst, align 4
+  %r = load atomic i32* %x.addr seq_cst, align 4
+  ret i32 %r
+}
+
+; A function with an Acquire load is not readonly.
+define i32 @test2(i32* %x) uwtable ssp {
+; CHECK: define i32 @test2(i32 %x) uwtable ssp {
+entry:
+  %r = load atomic i32* %x seq_cst, align 4
+  ret i32 %r
+}
+