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Generate more efficient for regular varying 'if' statements.

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For the case where we have a regular (i.e. non-'cif') 'if' statement,
the generated code just simply checks to see if any program instance
is running before running the corresponding statements.  This is a
lighter-weight check than IfStmt::emitMaskMixed() was performing.
This commit is contained in:
Matt Pharr
2011-09-16 12:03:42 -07:00
parent 1dedd88132
commit 173632f446
2 changed files with 42 additions and 11 deletions
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52
stmt.cpp
View File

@@ -405,9 +405,9 @@ DeclStmt::Print(int indent) const {
IfStmt::IfStmt(Expr *t, Stmt *ts, Stmt *fs, bool checkCoherence, SourcePos p) IfStmt::IfStmt(Expr *t, Stmt *ts, Stmt *fs, bool checkCoherence, SourcePos p)
: Stmt(p), test(t), trueStmts(ts), falseStmts(fs), : Stmt(p), test(t), trueStmts(ts), falseStmts(fs),
doAllCheck(checkCoherence && doAllCheck(checkCoherence &&
(test->GetType() != NULL) && !g->opt.disableCoherentControlFlow),
test->GetType()->IsVaryingType() && doAnyCheck(test->GetType() != NULL &&
!g->opt.disableCoherentControlFlow) { test->GetType()->IsVaryingType()) {
} }
@@ -541,7 +541,7 @@ IfStmt::Print(int indent) const {
/** Emit code to run both the true and false statements for the if test, /** Emit code to run both the true and false statements for the if test,
with the mask set appropriately before runnign each one. with the mask set appropriately before running each one.
*/ */
void void
IfStmt::emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask, IfStmt::emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask,
@@ -606,15 +606,45 @@ IfStmt::emitVaryingIf(FunctionEmitContext *ctx, llvm::Value *ltest) const {
// paths above jump to when they're done. // paths above jump to when they're done.
ctx->SetCurrentBasicBlock(bDone); ctx->SetCurrentBasicBlock(bDone);
} }
else { else if (trueStmts != NULL || falseStmts != NULL) {
llvm::BasicBlock *bDone = ctx->CreateBasicBlock("cif_done"); assert(doAnyCheck);
// Emit emit code for the mixed mask case ctx->StartVaryingIf(oldMask);
emitMaskMixed(ctx, oldMask, ltest, bDone); llvm::BasicBlock *bNext = ctx->CreateBasicBlock("safe_if_after_true");
if (trueStmts != NULL) {
llvm::BasicBlock *bRunTrue = ctx->CreateBasicBlock("safe_if_run_true");
ctx->MaskAnd(oldMask, ltest);
// When done, set the current basic block to the block that the two // Do any of the program instances want to run the 'true'
// paths above jump to when they're done. // block? If not, jump ahead to bNext.
ctx->SetCurrentBasicBlock(bDone); llvm::Value *maskAnyQ = ctx->Any(ctx->GetMask());
ctx->BranchInst(bRunTrue, bNext, maskAnyQ);
// Emit statements for true
ctx->SetCurrentBasicBlock(bRunTrue);
lEmitIfStatements(ctx, trueStmts, "if: expr mixed, true statements");
assert(ctx->GetCurrentBasicBlock());
ctx->BranchInst(bNext);
ctx->SetCurrentBasicBlock(bNext);
}
if (falseStmts != NULL) {
llvm::BasicBlock *bRunFalse = ctx->CreateBasicBlock("safe_if_run_false");
bNext = ctx->CreateBasicBlock("safe_if_after_false");
ctx->MaskAndNot(oldMask, ltest);
// Similarly, check to see if any of the instances want to run
// run the 'false' block...
llvm::Value *maskAnyQ = ctx->Any(ctx->GetMask());
ctx->BranchInst(bRunFalse, bNext, maskAnyQ);
// Emit code for false
ctx->SetCurrentBasicBlock(bRunFalse);
lEmitIfStatements(ctx, falseStmts, "if: expr mixed, false statements");
assert(ctx->GetCurrentBasicBlock());
ctx->BranchInst(bNext);
ctx->SetCurrentBasicBlock(bNext);
}
ctx->EndIf();
} }
} }

1
stmt.h
View File

@@ -126,6 +126,7 @@ private:
active program instances want to follow just one of the 'true' or active program instances want to follow just one of the 'true' or
'false' blocks. */ 'false' blocks. */
const bool doAllCheck; const bool doAllCheck;
const bool doAnyCheck;
void emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask, void emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask,
llvm::Value *test) const; llvm::Value *test) const;