[llvm-commits] [llvm] r163106 - in /llvm/trunk: lib/Analysis/MemoryDependenceAnalysis.cpp test/Transforms/DeadStoreElimination/simple.ll

[Bob Wilson]

Author: bwilson
Date: Mon Sep  3 00:15:15 2012
New Revision: 163106

URL: http://llvm.org/viewvc/llvm-project?rev=163106&view=rev
Log:
Fix more fallout from r158919, similar to PR13547.

This code used to only handle malloc-like calls, which do not read memory.
r158919 changed it to check isNoAliasFn(), which includes strdup-like and
realloc-like calls, but it was not checking for dependencies on the memory
read by those calls.

Modified:
    llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp
    llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll

Modified: llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp?rev=163106&r1=163105&r2=163106&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/MemoryDependenceAnalysis.cpp Mon Sep  3 00:15:15 2012
@@ -479,12 +479,17 @@
     // a subsequent bitcast of the malloc call result.  There can be stores to
     // the malloced memory between the malloc call and its bitcast uses, and we
     // need to continue scanning until the malloc call.
-    if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, AA->getTargetLibraryInfo())){
+    const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo();
+    if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) {
       const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD);
       
       if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
         return MemDepResult::getDef(Inst);
-      continue;
+      // If the allocation is not aliased and does not read memory (like
+      // strdup), it is safe to ignore.
+      if (isa<AllocaInst>(Inst) ||
+          isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI))
+        continue;
     }
 
     // See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.

Modified: llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll?rev=163106&r1=163105&r2=163106&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll (original)
+++ llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll Mon Sep  3 00:15:15 2012
@@ -310,3 +310,17 @@
   store i32 %c, i32* %4, align 4
   ret void
 }
+
+; Check another case like PR13547 where strdup is not like malloc.
+; CHECK: @test25
+; CHECK: load i8
+; CHECK: store i8 0
+; CHECK: store i8 %tmp
+define i8* @test25(i8* %p) nounwind {
+  %p.4 = getelementptr i8* %p, i64 4
+  %tmp = load i8* %p.4, align 1
+  store i8 0, i8* %p.4, align 1
+  %q = call i8* @strdup(i8* %p) nounwind optsize
+  store i8 %tmp, i8* %p.4, align 1
+  ret i8* %q
+}