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Don't check for "all off" mask at function entry.

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We should never be running with an all off mask and thus should never
enter a function with an all off mask.  No performance change from
removing this, however.

Issue #282.
This commit is contained in:
Matt Pharr
2012-06-15 10:14:39 -07:00
parent 4945dc3682
commit f47171a17c
1 changed files with 7 additions and 19 deletions
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26
func.cpp
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@@ -304,12 +304,12 @@ Function::emitCode(FunctionEmitContext *ctx, llvm::Function *function,
llvm::Value *mask = ctx->GetFunctionMask();
llvm::Value *allOn = ctx->All(mask);
llvm::BasicBlock *bbAllOn = ctx->CreateBasicBlock("all_on");
llvm::BasicBlock *bbNotAll = ctx->CreateBasicBlock("not_all_on");
llvm::BasicBlock *bbSomeOn = ctx->CreateBasicBlock("some_on");
// Set up basic blocks for goto targets
ctx->InitializeLabelMap(code);
ctx->BranchInst(bbAllOn, bbNotAll, allOn);
ctx->BranchInst(bbAllOn, bbSomeOn, allOn);
// all on: we've determined dynamically that the mask is all
// on. Set the current mask to "all on" explicitly so that
// codegen for this path can be improved with this knowledge in
@@ -321,23 +321,11 @@ Function::emitCode(FunctionEmitContext *ctx, llvm::Function *function,
if (ctx->GetCurrentBasicBlock())
ctx->ReturnInst();
// not all on: figure out if no instances are running, or if
// some of them are
ctx->SetCurrentBasicBlock(bbNotAll);
ctx->SetFunctionMask(mask);
llvm::BasicBlock *bbNoneOn = ctx->CreateBasicBlock("none_on");
llvm::BasicBlock *bbSomeOn = ctx->CreateBasicBlock("some_on");
llvm::Value *anyOn = ctx->Any(mask);
ctx->BranchInst(bbSomeOn, bbNoneOn, anyOn);
// Everyone is off; get out of here.
ctx->SetCurrentBasicBlock(bbNoneOn);
ctx->ReturnInst();
// some on: reset the mask to the value it had at function
// entry and emit the code. Resetting the mask here is
// important, due to the "all on" setting of it for the path
// above
// not all on: however, at least one lane must be running,
// since we should never run with all off... some on: reset
// the mask to the value it had at function entry and emit the
// code. Resetting the mask here is important, due to the "all
// on" setting of it for the path above.
ctx->SetCurrentBasicBlock(bbSomeOn);
ctx->SetFunctionMask(mask);