[llvm-commits] [llvm] r44981 - in /llvm/trunk: lib/Transforms/Scalar/CodeGenPrepare.cpp test/CodeGen/X86/opt-ext-uses.ll

[Evan Cheng]

Author: evancheng
Date: Wed Dec 12 21:32:53 2007
New Revision: 44981

URL: http://llvm.org/viewvc/llvm-project?rev=44981&view=rev
Log:
Be extra careful with extension use optimation. Now turned on by default.

Modified:
    llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
    llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll

Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=44981&r1=44980&r2=44981&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Wed Dec 12 21:32:53 2007
@@ -36,7 +36,7 @@
 
 namespace {
   cl::opt<bool> OptExtUses("optimize-ext-uses",
-                           cl::init(false), cl::Hidden);
+                           cl::init(true), cl::Hidden);
 }
 
 namespace {  
@@ -929,6 +929,10 @@
   if (Src->hasOneUse())
     return false;
 
+  // Only do this xform is truncating is free.
+  if (!TLI->isTruncateFree(I->getType(), Src->getType()))
+    return false;
+
   // Only safe to perform the optimization if the source is also defined in
   // this block.
   if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
@@ -952,8 +956,11 @@
   for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); 
        UI != E; ++UI) {
     Instruction *User = cast<Instruction>(*UI);
-    if (User->getParent() == DefBB) continue;
-    if (isa<PHINode>(User))
+    BasicBlock *UserBB = User->getParent();
+    if (UserBB == DefBB) continue;
+    // Be conservative. We don't want this xform to end up introducing
+    // reloads just before load / store instructions.
+    if (isa<PHINode>(User) || isa<LoadInst>(User) || isa<StoreInst>(User))
       return false;
   }
 

Modified: llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll?rev=44981&r1=44980&r2=44981&view=diff

==============================================================================
--- llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll (original)
+++ llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll Wed Dec 12 21:32:53 2007
@@ -1,4 +1,4 @@
-; RUN: llvm-as < %s | llc -march=x86 -optimize-ext-uses=true | grep movw | count 1
+; RUN: llvm-as < %s | llc -march=x86 | grep movw | count 1
 
 define i16 @t() signext  {
 entry: