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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
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@ -63,15 +63,6 @@ static cl::opt<bool>
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DisablePromotion("disable-licm-promotion", cl::Hidden,
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DisablePromotion("disable-licm-promotion", cl::Hidden,
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cl::desc("Disable memory promotion in LICM pass"));
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cl::desc("Disable memory promotion in LICM pass"));
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// This feature is currently disabled by default because CodeGen is not yet
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// capable of rematerializing these constants in PIC mode, so it can lead to
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// degraded performance. Compile test/CodeGen/X86/remat-constant.ll with
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// -relocation-model=pic to see an example of this.
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static cl::opt<bool>
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EnableLICMConstantMotion("enable-licm-constant-variables", cl::Hidden,
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cl::desc("Enable hoisting/sinking of constant "
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"global variables"));
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namespace {
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namespace {
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struct LICM : public LoopPass {
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struct LICM : public LoopPass {
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static char ID; // Pass identification, replacement for typeid
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static char ID; // Pass identification, replacement for typeid
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@ -383,8 +374,7 @@ bool LICM::canSinkOrHoistInst(Instruction &I) {
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// Loads from constant memory are always safe to move, even if they end up
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// Loads from constant memory are always safe to move, even if they end up
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// in the same alias set as something that ends up being modified.
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// in the same alias set as something that ends up being modified.
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if (EnableLICMConstantMotion &&
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if (AA->pointsToConstantMemory(LI->getOperand(0)))
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AA->pointsToConstantMemory(LI->getOperand(0)))
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return true;
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return true;
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// Don't hoist loads which have may-aliased stores in loop.
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// Don't hoist loads which have may-aliased stores in loop.
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@ -1,4 +1,4 @@
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; RUN: opt < %s -licm -enable-licm-constant-variables -S | FileCheck %s
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; RUN: opt < %s -licm -S | FileCheck %s
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@a = external constant float*
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@a = external constant float*
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