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Be extra careful with extension use optimation. Now turned on by default.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44981 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-12-13 03:32:53 +00:00
parent bd4d6b8564
commit f9785f92b6
2 changed files with 11 additions and 4 deletions
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13
lib/Transforms/Scalar/CodeGenPrepare.cpp
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@ -36,7 +36,7 @@ using namespace llvm;
namespace { namespace {
cl::opt<bool> OptExtUses("optimize-ext-uses", cl::opt<bool> OptExtUses("optimize-ext-uses",
cl::init(false), cl::Hidden); cl::init(true), cl::Hidden);
} }
namespace { namespace {
@ -929,6 +929,10 @@ bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
if (Src->hasOneUse()) if (Src->hasOneUse())
return false; 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 // Only safe to perform the optimization if the source is also defined in
// this block. // this block.
if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent()) if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)->getParent())
@ -952,8 +956,11 @@ bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
UI != E; ++UI) { UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI); Instruction *User = cast<Instruction>(*UI);
if (User->getParent() == DefBB) continue; BasicBlock *UserBB = User->getParent();
if (isa<PHINode>(User)) 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; return false;
} }

2
test/CodeGen/X86/opt-ext-uses.ll
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@ -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 { define i16 @t() signext {
entry: entry: