On Dec 12, 2007, at 8:40 PM, Chris Lattner wrote: > On Dec 12, 2007, at 7:32 PM, Evan Cheng wrote: > >> Author: evancheng >> Date: Wed Dec 12 21:32:53 2007 >> New Revision: 44981 >> >> URL: http://llvm.org/viewvc/llvm-project?rev=44981&view=rev >> Log: >> Be extra careful with extension use optimation. Now turned on by >> default. > > FYI, on your testcase with -print-isel-input, it looks like multiple > instructions are sunk: > > > cond_true188: ; preds = %entry > trunc i32 %tmp180181 to i16 ; <i16>:0 [#uses=1] > trunc i32 %tmp180181 to i16 ; <i16>:1 [#uses=1] > %tmp195196 = trunc i16 %0 to i8 ; <i8> [#uses=0] > ret i16 %1 > > Is this desired?
No it's not. I'll look. Evan > > -Chris > >> >> >> Modified: >> llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp >> llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll >> >> Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp >> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/ >> Scalar/CodeGenPrepare.cpp?rev=44981&r1=44980&r2=44981&view=diff >> >> = >> = >> = >> = >> = >> = >> = >> = >> ===================================================================== >> = >> --- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original) >> +++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Wed Dec 12 >> 21:32:53 2007 >> @@ -36,7 +36,7 @@ >> >> namespace { >> cl::opt<bool> OptExtUses("optimize-ext-uses", >> - cl::init(false), cl::Hidden); >> + cl::init(true), cl::Hidden); >> } >> >> namespace { >> @@ -929,6 +929,10 @@ >> if (Src->hasOneUse()) >> 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 >> // this block. >> if (!isa<Instruction>(Src) || DefBB != cast<Instruction>(Src)- >>> getParent()) >> @@ -952,8 +956,11 @@ >> for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end(); >> UI != E; ++UI) { >> Instruction *User = cast<Instruction>(*UI); >> - if (User->getParent() == DefBB) continue; >> - if (isa<PHINode>(User)) >> + BasicBlock *UserBB = User->getParent(); >> + 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; >> } >> >> >> Modified: llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll >> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ >> X86/opt-ext-uses.ll?rev=44981&r1=44980&r2=44981&view=diff >> >> = >> = >> = >> = >> = >> = >> = >> = >> ===================================================================== >> = >> --- llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll (original) >> +++ llvm/trunk/test/CodeGen/X86/opt-ext-uses.ll Wed Dec 12 21:32:53 >> 2007 >> @@ -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 { >> entry: >> >> >> _______________________________________________ >> llvm-commits mailing list >> llvm-commits@cs.uiuc.edu >> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits > > _______________________________________________ > llvm-commits mailing list > llvm-commits@cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
