[llvm-commits] [llvm] r132288 - in /llvm/trunk: lib/Transforms/IPO/GlobalOpt.cpp test/Transforms/GlobalOpt/memset-null.ll

[Nick Lewycky]

Author: nicholas
Date: Sun May 29 13:41:56 2011
New Revision: 132288

URL: http://llvm.org/viewvc/llvm-project?rev=132288&view=rev
Log:
Obey the isVolatile bit on memory intrinsics when analyzing uses of a global
variable. Noticed by inspection.

Simulate memset in EvaluateFunction where the target of the memset and the
value we're setting are both the null value. Fixes PR10047!

Added:
    llvm/trunk/test/Transforms/GlobalOpt/memset-null.ll
Modified:
    llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp

Modified: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=132288&r1=132287&r2=132288&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp Sun May 29 13:41:56 2011
@@ -241,15 +241,15 @@
         GS.HasPHIUser = true;
       } else if (isa<CmpInst>(I)) {
         GS.isCompared = true;
-      } else if (isa<MemTransferInst>(I)) {
-        const MemTransferInst *MTI = cast<MemTransferInst>(I);
+      } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
+        if (MTI->isVolatile()) return true;
         if (MTI->getArgOperand(0) == V)
           GS.StoredType = GlobalStatus::isStored;
         if (MTI->getArgOperand(1) == V)
           GS.isLoaded = true;
-      } else if (isa<MemSetInst>(I)) {
-        assert(cast<MemSetInst>(I)->getArgOperand(0) == V &&
-               "Memset only takes one pointer!");
+      } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
+        assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
+        if (MSI->isVolatile()) return true;
         GS.StoredType = GlobalStatus::isStored;
       } else {
         return true;  // Any other non-load instruction might take address!
@@ -2438,6 +2438,20 @@
       // Cannot handle inline asm.
       if (isa<InlineAsm>(CI->getCalledValue())) return false;
 
+      if (MemSetInst *MSI = dyn_cast<MemSetInst>(CI)) {
+        if (MSI->isVolatile()) return false;
+        Constant *Ptr = getVal(Values, MSI->getDest());
+        Constant *Val = getVal(Values, MSI->getValue());
+        Constant *DestVal = ComputeLoadResult(getVal(Values, Ptr),
+                                              MutatedMemory);
+        if (Val->isNullValue() && DestVal->isNullValue()) {
+          // This memset is a no-op.
+          ++CurInst;
+          continue;
+        }
+        return false;
+      }
+
       // Resolve function pointers.
       Function *Callee = dyn_cast<Function>(getVal(Values,
                                                    CI->getCalledValue()));

Added: llvm/trunk/test/Transforms/GlobalOpt/memset-null.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GlobalOpt/memset-null.ll?rev=132288&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GlobalOpt/memset-null.ll (added)
+++ llvm/trunk/test/Transforms/GlobalOpt/memset-null.ll Sun May 29 13:41:56 2011
@@ -0,0 +1,19 @@
+; RUN: opt -globalopt %s -S -o - | FileCheck %s
+; PR10047
+
+
+%0 = type { i32, void ()* }
+%struct.A = type { [100 x i32] }
+
+; CHECK: @a
+ at a = global %struct.A zeroinitializer, align 4
+ at llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @_GLOBAL__I_a }]
+
+declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
+
+; CHECK-NOT: GLOBAL__I_a
+define internal void @_GLOBAL__I_a() nounwind {
+entry:
+  tail call void @llvm.memset.p0i8.i64(i8* bitcast (%struct.A* @a to i8*), i8 0, i64 400, i32 4, i1 false) nounwind
+  ret void
+}