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Actually make all 'if' statements check for 'all off' mask.

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Contrary to claims in 0c2048385, that checkin didn't include the changes
to not run if/else blocks if none of the program instances wanted to be
running them.  This checkin fixes that and thus actually fixes issue #74.
This commit is contained in:
Matt Pharr
2011-09-13 19:48:04 -07:00
parent e2a88d491f
commit 0848c2cc19
2 changed files with 48 additions and 54 deletions
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96
stmt.cpp
View File

@@ -404,10 +404,10 @@ DeclStmt::Print(int indent) const {
IfStmt::IfStmt(Expr *t, Stmt *ts, Stmt *fs, bool checkCoherence, SourcePos p)
: Stmt(p), test(t), trueStmts(ts), falseStmts(fs),
doCoherentCheck(checkCoherence &&
(test->GetType() != NULL) &&
test->GetType()->IsVaryingType() &&
!g->opt.disableCoherentControlFlow) {
doAllCheck(checkCoherence &&
(test->GetType() != NULL) &&
test->GetType()->IsVaryingType() &&
!g->opt.disableCoherentControlFlow) {
}
@@ -439,62 +439,46 @@ IfStmt::EmitCode(FunctionEmitContext *ctx) const {
ctx->SetDebugPos(pos);
bool isUniform = testType->IsUniformType();
llvm::Value *testValue = test->GetValue(ctx);
if (testValue == NULL)
return;
if (isUniform) {
ctx->StartUniformIf(ctx->GetMask());
if (doCoherentCheck)
if (doAllCheck)
Warning(test->pos, "Uniform condition supplied to \"cif\" statement.");
// 'If' statements with uniform conditions are relatively
// straightforward. We evaluate the condition and then jump to
// either the 'then' or 'else' clause depending on its value.
llvm::Value *vtest = test->GetValue(ctx);
if (vtest != NULL) {
llvm::BasicBlock *bthen = ctx->CreateBasicBlock("if_then");
llvm::BasicBlock *belse = ctx->CreateBasicBlock("if_else");
llvm::BasicBlock *bexit = ctx->CreateBasicBlock("if_exit");
llvm::BasicBlock *bthen = ctx->CreateBasicBlock("if_then");
llvm::BasicBlock *belse = ctx->CreateBasicBlock("if_else");
llvm::BasicBlock *bexit = ctx->CreateBasicBlock("if_exit");
// Jump to the appropriate basic block based on the value of
// the 'if' test
ctx->BranchInst(bthen, belse, vtest);
// Jump to the appropriate basic block based on the value of
// the 'if' test
ctx->BranchInst(bthen, belse, testValue);
// Emit code for the 'true' case
ctx->SetCurrentBasicBlock(bthen);
lEmitIfStatements(ctx, trueStmts, "true");
if (ctx->GetCurrentBasicBlock())
ctx->BranchInst(bexit);
// Emit code for the 'true' case
ctx->SetCurrentBasicBlock(bthen);
lEmitIfStatements(ctx, trueStmts, "true");
if (ctx->GetCurrentBasicBlock())
ctx->BranchInst(bexit);
// Emit code for the 'false' case
ctx->SetCurrentBasicBlock(belse);
lEmitIfStatements(ctx, falseStmts, "false");
if (ctx->GetCurrentBasicBlock())
ctx->BranchInst(bexit);
// Emit code for the 'false' case
ctx->SetCurrentBasicBlock(belse);
lEmitIfStatements(ctx, falseStmts, "false");
if (ctx->GetCurrentBasicBlock())
ctx->BranchInst(bexit);
// Set the active basic block to the newly-created exit block
// so that subsequent emitted code starts there.
ctx->SetCurrentBasicBlock(bexit);
}
// Set the active basic block to the newly-created exit block
// so that subsequent emitted code starts there.
ctx->SetCurrentBasicBlock(bexit);
ctx->EndIf();
}
else {
// Code for 'If' statemnts with 'varying' conditions can be
// generated in two ways; one takes some care to see if all of the
// active program instances want to follow only the 'true' or
// 'false' cases, and the other always runs both cases but sets the
// mask appropriately. The first case is handled by the
// IfStmt::emitCoherentTests() call, and the second is handled by
// IfStmt::emitMaskedTrueAndFalse().
llvm::Value *testValue = test->GetValue(ctx);
if (testValue) {
if (doCoherentCheck)
emitCoherentTests(ctx, testValue);
else {
llvm::Value *oldMask = ctx->GetMask();
ctx->StartVaryingIf(oldMask);
emitMaskedTrueAndFalse(ctx, oldMask, testValue);
ctx->EndIf();
}
}
}
else
emitVaryingIf(ctx, testValue);
}
@@ -540,7 +524,7 @@ Stmt *IfStmt::TypeCheck() {
void
IfStmt::Print(int indent) const {
printf("%*cIf Stmt %s", indent, ' ', doCoherentCheck ? "DO COHERENT CHECK" : "");
printf("%*cIf Stmt %s", indent, ' ', doAllCheck ? "DO ALL CHECK" : "");
pos.Print();
printf("\n%*cTest: ", indent+4, ' ');
test->Print();
@@ -581,7 +565,7 @@ IfStmt::emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask,
tries to be smart about jumping over code that doesn't need to be run.
*/
void
IfStmt::emitCoherentTests(FunctionEmitContext *ctx, llvm::Value *ltest) const {
IfStmt::emitVaryingIf(FunctionEmitContext *ctx, llvm::Value *ltest) const {
llvm::Value *oldMask = ctx->GetMask();
if (oldMask == LLVMMaskAllOn) {
// We can tell that the mask is on statically at compile time; just
@@ -590,7 +574,7 @@ IfStmt::emitCoherentTests(FunctionEmitContext *ctx, llvm::Value *ltest) const {
emitMaskAllOn(ctx, ltest, bDone);
ctx->SetCurrentBasicBlock(bDone);
}
else {
else if (doAllCheck) {
// We can't tell if the mask going into the if is all on at the
// compile time. Emit code to check for this and then either run
// the code for the 'all on' or the 'mixed' case depending on the
@@ -618,6 +602,16 @@ IfStmt::emitCoherentTests(FunctionEmitContext *ctx, llvm::Value *ltest) const {
ctx->SetCurrentBasicBlock(bMixedOn);
emitMaskMixed(ctx, oldMask, ltest, bDone);
// When done, set the current basic block to the block that the two
// paths above jump to when they're done.
ctx->SetCurrentBasicBlock(bDone);
}
else {
llvm::BasicBlock *bDone = ctx->CreateBasicBlock("cif_done");
// Emit emit code for the mixed mask case
emitMaskMixed(ctx, oldMask, ltest, bDone);
// When done, set the current basic block to the block that the two
// paths above jump to when they're done.
ctx->SetCurrentBasicBlock(bDone);
@@ -701,7 +695,7 @@ IfStmt::emitMaskMixed(FunctionEmitContext *ctx, llvm::Value *oldMask,
// value of the test is on. (i.e. (test&mask) == mask). In this case,
// we only need to run the 'true' case code, since the lanes where the
// test was false aren't supposed to be running here anyway.
llvm::Value *testAllEqual = lTestMatchesMask(ctx, ltest, oldMask);
llvm::Value *testAllEqual = lTestMatchesMask(ctx, ltest, oldMask);
llvm::BasicBlock *bTestAll = ctx->CreateBasicBlock("cif_mixed_test_all");
llvm::BasicBlock *bTestAnyCheck = ctx->CreateBasicBlock("cif_mixed_test_any_check");
ctx->BranchInst(bTestAll, bTestAnyCheck, testAllEqual);

6
stmt.h
View File

@@ -103,7 +103,7 @@ private:
class IfStmt : public Stmt {
public:
IfStmt(Expr *testExpr, Stmt *trueStmts, Stmt *falseStmts,
bool doCoherentCheck, SourcePos pos);
bool doAllCheck, SourcePos pos);
void EmitCode(FunctionEmitContext *ctx) const;
void Print(int indent) const;
@@ -125,11 +125,11 @@ private:
source and thus, if the emitted code should check to see if all
active program instances want to follow just one of the 'true' or
'false' blocks. */
const bool doCoherentCheck;
const bool doAllCheck;
void emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask,
llvm::Value *test) const;
void emitCoherentTests(FunctionEmitContext *ctx, llvm::Value *test) const;
void emitVaryingIf(FunctionEmitContext *ctx, llvm::Value *test) const;
void emitMaskAllOn(FunctionEmitContext *ctx,
llvm::Value *test, llvm::BasicBlock *bDone) const;
void emitMaskMixed(FunctionEmitContext *ctx, llvm::Value *oldMask,