Author: [email protected]
Date: Tue Feb 24 01:21:25 2009
New Revision: 1344
Modified:
branches/experimental/toiger/src/codegen-ia32.cc
Log:
Experimental: restore the test at the bottom of for and while loops.
In order to satisfy the requirement that a virtual frame has to reach
the body when we compile it, the test is duplicated and appears at
both the top and bottom of the loop.
Review URL: http://codereview.chromium.org/27084
Modified: branches/experimental/toiger/src/codegen-ia32.cc
==============================================================================
--- branches/experimental/toiger/src/codegen-ia32.cc (original)
+++ branches/experimental/toiger/src/codegen-ia32.cc Tue Feb 24 01:21:25
2009
@@ -2249,46 +2249,72 @@
}
case LoopStatement::WHILE_LOOP: {
+ JumpTarget body(this, JumpTarget::BIDIRECTIONAL);
IncrementLoopNesting();
- // If the test is never true and has no side effects there is no need
- // to compile the test or body.
+ // If the condition is always false and has no side effects, we
+ // do not need to compile anything.
if (info == ALWAYS_FALSE) break;
- // Label the top of the loop with the continue target for the
backward
- // CFG edge.
- node->continue_target()->Initialize(this, JumpTarget::BIDIRECTIONAL);
- node->continue_target()->Bind();
-
- // If the test is always true and has no side effects there is no
need
- // to compile it. We only compile the test when we do not know its
- // outcome or it may have side effects.
- JumpTarget body(this);
- ControlDestination dest(&body, node->break_target(), true);
- if (info == DONT_KNOW) {
+ // Based on the condition analysis, compile the test if
+ // necessary and label the body if necessary.
+ if (info == ALWAYS_TRUE) {
+ // We will not compile the test expression. Label the top of
+ // the loop with the continue target.
+ node->continue_target()->Initialize(this,
JumpTarget::BIDIRECTIONAL);
+ node->continue_target()->Bind();
+ } else {
+ ASSERT(info == DONT_KNOW); // ALWAYS_FALSE cannot reach here.
+ node->continue_target()->Initialize(this);
+ // Compile the test with the body as the true target and
+ // preferred fall-through and with the break target as the
+ // false target.
+ ControlDestination dest(&body, node->break_target(), true);
LoadCondition(node->cond(), NOT_INSIDE_TYPEOF, &dest, true);
- }
- if (dest.false_was_fall_through()) {
- // The break target was bound. We may have dangling jumps to
- // the body.
- if (!body.is_linked()) break;
-
- // We have dangling jumps to the body target.
- node->break_target()->Unuse();
- node->break_target()->Jump();
- body.Bind();
+ if (dest.false_was_fall_through()) {
+ // If we don't have dangling jumps to the body, the test is
+ // unconditionally false and we do not need to compile the
+ // body.
+ if (!body.is_linked()) break;
+
+ // Otherwise, jump around the body on the fall through and
+ // then bind the body target.
+ node->break_target()->Unuse();
+ node->break_target()->Jump();
+ body.Bind();
+ }
}
- // The body target has just been bound or else we didn't compile
- // the test.
+ // The (stack check at the start of the) body was labeled.
+ // Compile it.
CheckStack(); // TODO(1222600): ignore if body contains calls.
Visit(node->body());
- // If control flow can fall out of the body, jump back to the top.
- if (has_valid_frame()) {
- node->continue_target()->Jump();
+ // Compile the test if necessary and jump back.
+ if (info == ALWAYS_TRUE) {
+ // The body has been labeled with the continue target.
+ if (has_valid_frame()) {
+ node->continue_target()->Jump();
+ }
+ } else {
+ ASSERT(info == DONT_KNOW); // ALWAYS_FALSE cannot reach here.
+ if (node->continue_target()->is_linked()) {
+ node->continue_target()->Bind();
+ }
+
+ // If control can reach the bottom by falling off the body or
+ // a continue in the body, (re)compile the test at the bottom.
+ if (has_valid_frame()) {
+ // The break target is the fall-through (body is a backward
+ // jump from here).
+ ControlDestination dest(&body, node->break_target(), false);
+ LoadCondition(node->cond(), NOT_INSIDE_TYPEOF, &dest, true);
+ }
}
+
+ // The break target may be already bound (by the condition), or
+ // there may not be a valid frame. Bind it only if needed.
if (node->break_target()->is_linked()) {
node->break_target()->Bind();
}
@@ -2296,80 +2322,111 @@
}
case LoopStatement::FOR_LOOP: {
- JumpTarget loop(this, JumpTarget::BIDIRECTIONAL);
+ JumpTarget body(this, JumpTarget::BIDIRECTIONAL);
+
+ // Compile the init expression if present.
if (node->init() != NULL) {
Visit(node->init());
}
IncrementLoopNesting();
- // If the test is never true and has no side effects there is no need
- // to compile the test or body.
+
+ // If the condition is always false and has no side effects, we
+ // do not need to compile anything else.
if (info == ALWAYS_FALSE) break;
- // Label the top of the loop for the backward CFG edge. If there is
- // no update expression we can use the continue target.
- if (node->next() == NULL) {
- node->continue_target()->Initialize(this,
JumpTarget::BIDIRECTIONAL);
- node->continue_target()->Bind();
+ // Based on the condition analysis, compile the test if
+ // necessary and label the body if necessary.
+ if (info == ALWAYS_TRUE) {
+ // We will not compile the test expression. Label the top of
+ // the loop with the continue target if there is no update
+ // expression, otherwise with the body target.
+ if (node->next() == NULL) {
+ node->continue_target()->Initialize(this,
JumpTarget::BIDIRECTIONAL);
+ node->continue_target()->Bind();
+ } else {
+ node->continue_target()->Initialize(this);
+ body.Bind();
+ }
} else {
+ ASSERT(info == DONT_KNOW);
node->continue_target()->Initialize(this);
- loop.Bind();
- }
-
- // If the test is always true and has no side effects there is no
need
- // to compile it. We only compile the test when we do not know its
- // outcome or it has side effects.
- JumpTarget body(this);
- ControlDestination dest(&body, node->break_target(), true);
- if (info == DONT_KNOW) {
+ // Compile the test with the body as the true target and
+ // preferred fall-through and with the break target as the
+ // false target.
+ ControlDestination dest(&body, node->break_target(), true);
LoadCondition(node->cond(), NOT_INSIDE_TYPEOF, &dest, true);
- }
- if (dest.false_was_fall_through()) {
- // The break target was bound. We may have dangling jumps to
- // the body.
- if (!body.is_linked()) break;
-
- node->break_target()->Unuse();
- node->break_target()->Jump();
- body.Bind();
+ if (dest.false_was_fall_through()) {
+ // If we don't have dangling jumps to the body, the test is
+ // unconditionally false and we do not need to compile the
+ // body.
+ if (!body.is_linked()) break;
+
+ // Otherwise, jump around the body on the fall through and
+ // then bind the body target.
+ node->break_target()->Unuse();
+ node->break_target()->Jump();
+ body.Bind();
+ }
}
- // The body target has just been bound or else we didn't compile
- // the test.
+ // The (stack check at the start of the) body was labeled.
+ // Compile it.
CheckStack(); // TODO(1222600): ignore if body contains calls.
Visit(node->body());
- if (node->next() == NULL) {
- // If there is no update statement and control flow can fall out
- // of the loop, jump to the continue label.
- if (has_valid_frame()) {
- node->continue_target()->Jump();
+ // If there is an update expression, compile it if necessary.
+ if (node->next() != NULL) {
+ // We did not use the continue target for the body.
+ if (node->continue_target()->is_linked()) {
+ node->continue_target()->Bind();
}
- if (node->break_target()->is_linked()) {
- node->break_target()->Bind();
+
+ // Control can reach the update by falling out of the body or
+ // by a continue in the body.
+ if (has_valid_frame()) {
+ // Record the source position of the statement as this code
+ // which is after the code for the body actually belongs to
+ // the loop statement and not the body.
+ CodeForStatementPosition(node);
+ Visit(node->next());
}
+ }
+ // Compile the test if necessary and jump back.
+ if (info == ALWAYS_TRUE) {
+ if (has_valid_frame()) {
+ if (node->next() == NULL) {
+ node->continue_target()->Jump();
+ } else {
+ body.Jump();
+ }
+ }
} else {
- // If there is an update statement and control flow can reach it
- // via falling out of the body of the loop or continuing, we
- // compile the update statement.
+ ASSERT(info == DONT_KNOW); // ALWAYS_FALSE cannot reach here.
if (node->continue_target()->is_linked()) {
+ // We can have dangling jumps to the continue target if
+ // there was no update expression.
node->continue_target()->Bind();
}
+
+ // Control can reach the test at the bottom by falling out of
+ // the body, by a continue in the body, or from the update
+ // expression.
if (has_valid_frame()) {
- // Record source position of the statement as this code which is
- // after the code for the body actually belongs to the loop
- // statement and not the body.
- CodeForStatementPosition(node);
- Visit(node->next());
- loop.Jump();
- }
- if (node->break_target()->is_linked()) {
- node->break_target()->Bind();
+ // The break target is the fall-through (body is a backward
+ // jump from here).
+ ControlDestination dest(&body, node->break_target(), false);
+ LoadCondition(node->cond(), NOT_INSIDE_TYPEOF, &dest, true);
}
}
+ // The break target may be already bound (by the condition), or
+ // there may not be a valid frame. Bind it only if needed.
+ if (node->break_target()->is_linked()) {
+ node->break_target()->Bind();
+ }
break;
}
}
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