command-line option, and disable it by default. It introduced performance
regressions because CodeGen is currently not able to remat such loads.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53997
91177308-0d34-0410-b5e6-
96231b3b80d8
DisablePromotion("disable-licm-promotion", cl::Hidden,
cl::desc("Disable memory promotion in LICM pass"));
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 VISIBILITY_HIDDEN LICM : public LoopPass {
static char ID; // Pass identification, replacement for typeid
namespace {
struct VISIBILITY_HIDDEN LICM : public LoopPass {
static char ID; // Pass identification, replacement for typeid
// 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.
// 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 (AA->pointsToConstantMemory(LI->getOperand(0)))
+ if (EnableLICMConstantMotion &&
+ AA->pointsToConstantMemory(LI->getOperand(0)))
return true;
// Don't hoist loads which have may-aliased stores in loop.
return true;
// Don't hoist loads which have may-aliased stores in loop.
-; RUN: llvm-as < %s | opt -licm | llvm-dis | grep -A 1 entry | grep load.*@a
+; RUN: llvm-as < %s | opt -licm -enable-licm-constant-variables | llvm-dis | grep -A 1 entry | grep load.*@a
@a = external constant float*
define void @test(i32 %count) {
@a = external constant float*
define void @test(i32 %count) {