From dab249b3b762cff0ff16069b3233e4c885e75347 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Thu, 19 Nov 2009 19:00:10 +0000 Subject: [PATCH] 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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89374 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/LICM.cpp | 12 +----------- .../Transforms/LICM/2008-07-22-LoadGlobalConstant.ll | 2 +- 2 files changed, 2 insertions(+), 12 deletions(-) diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp index 104c8739c0e..a71b3e31e26 100644 --- a/lib/Transforms/Scalar/LICM.cpp +++ b/lib/Transforms/Scalar/LICM.cpp @@ -63,15 +63,6 @@ static cl::opt 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 -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 @@ bool LICM::canSinkOrHoistInst(Instruction &I) { // 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. diff --git a/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll b/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll index 723440f101e..10b00bab8fd 100644 --- a/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll +++ b/test/Transforms/LICM/2008-07-22-LoadGlobalConstant.ll @@ -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*