[llvm-commits] [llvm] r89374 - in /llvm/trunk: lib/Transforms/Scalar/LICM.cpp test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll

[Dan Gohman]

Author: djg
Date: Thu Nov 19 13:00:10 2009
New Revision: 89374

URL: http://llvm.org/viewvc/llvm-project?rev=89374&view=rev
Log:
Enable hoisting of loads from constant memory by default. In cases where
they are lowered to instruction sequences more complex than a simple
load, such that CodeGen cannot rematerialize them, a reload from a
spill slot is likely to be cheaper than the complex sequence.

Modified:
    llvm/trunk/lib/Transforms/Scalar/LICM.cpp
    llvm/trunk/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll

Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=89374&r1=89373&r2=89374&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Thu Nov 19 13:00:10 2009
@@ -63,15 +63,6 @@
 DisablePromotion("disable-licm-promotion", cl::Hidden,
                  cl::desc("Disable memory promotion in LICM pass"));
 
-// This feature is currently disabled by default because CodeGen is not yet
-// capable of rematerializing these constants in PIC mode, so it can lead to
-// degraded performance. Compile test/CodeGen/X86/remat-constant.ll with
-// -relocation-model=pic to see an example of this.
-static cl::opt<bool>
-EnableLICMConstantMotion("enable-licm-constant-variables", cl::Hidden,
-                         cl::desc("Enable hoisting/sinking of constant "
-                                  "global variables"));
-
 namespace {
   struct LICM : public LoopPass {
     static char ID; // Pass identification, replacement for typeid
@@ -383,8 +374,7 @@
 
     // Loads from constant memory are always safe to move, even if they end up
     // in the same alias set as something that ends up being modified.
-    if (EnableLICMConstantMotion &&
-        AA->pointsToConstantMemory(LI->getOperand(0)))
+    if (AA->pointsToConstantMemory(LI->getOperand(0)))
       return true;
     
     // Don't hoist loads which have may-aliased stores in loop.

Modified: llvm/trunk/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll?rev=89374&r1=89373&r2=89374&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll (original)
+++ llvm/trunk/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll Thu Nov 19 13:00:10 2009
@@ -1,4 +1,4 @@
-; RUN: opt < %s -licm -enable-licm-constant-variables -S | FileCheck %s
+; RUN: opt < %s -licm -S | FileCheck %s
 
 @a = external constant float*