[llvm-commits] [llvm] r161468 - in /llvm/trunk: lib/Transforms/Scalar/DeadStoreElimination.cpp test/Transforms/DeadStoreElimination/simple.ll

[Eli Friedman]

Author: efriedma
Date: Tue Aug  7 21:17:32 2012
New Revision: 161468

URL: http://llvm.org/viewvc/llvm-project?rev=161468&view=rev
Log:
isAllocLikeFn is allowed to return true for functions which read memory; make
sure we account for that correctly in DeadStoreElimination.  Fixes a regression
from r158919.  PR13547.


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

Modified: llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp?rev=161468&r1=161467&r2=161468&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp Tue Aug  7 21:17:32 2012
@@ -740,12 +740,19 @@
       continue;
     }
 
-    if (isa<AllocaInst>(BBI) || isAllocLikeFn(BBI)) {
+    if (isa<AllocaInst>(BBI)) {
+      // Remove allocas from the list of dead stack objects; there can't be
+      // any references before the definition.
       DeadStackObjects.remove(BBI);
       continue;
     }
 
     if (CallSite CS = cast<Value>(BBI)) {
+      // Remove allocation function calls from the list of dead stack objects; 
+      // there can't be any references before the definition.
+      if (isAllocLikeFn(BBI))
+        DeadStackObjects.remove(BBI);
+
       // If this call does not access memory, it can't be loading any of our
       // pointers.
       if (AA->doesNotAccessMemory(CS))
@@ -771,7 +778,7 @@
       // If all of the allocas were clobbered by the call then we're not going
       // to find anything else to process.
       if (DeadStackObjects.empty())
-        return MadeChange;
+        break;
 
       continue;
     }

Modified: llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll?rev=161468&r1=161467&r2=161468&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll (original)
+++ llvm/trunk/test/Transforms/DeadStoreElimination/simple.ll Tue Aug  7 21:17:32 2012
@@ -276,3 +276,18 @@
 ; CHECK-NEXT: ret void
   ret void
 }
+
+; PR13547
+; CHECK: @test23
+; CHECK: store i8 97
+; CHECK: store i8 0
+declare noalias i8* @strdup(i8* nocapture) nounwind
+define noalias i8* @test23() nounwind uwtable ssp {
+  %x = alloca [2 x i8], align 1
+  %arrayidx = getelementptr inbounds [2 x i8]* %x, i64 0, i64 0
+  store i8 97, i8* %arrayidx, align 1
+  %arrayidx1 = getelementptr inbounds [2 x i8]* %x, i64 0, i64 1
+  store i8 0, i8* %arrayidx1, align 1
+  %call = call i8* @strdup(i8* %arrayidx) nounwind
+  ret i8* %call
+}