Reviewers: jochen, ulan,
Description:
A64: Let the MacroAssembler resolve branches to distant targets.
Code generation would fail when assembling a branch to a label that is bound
outside the immediate range of the instruction. A64 is sensitive to this,
as the
various branching instructions have different ranges, going down to +-32KB
for
TBZ/TBNZ. The MacroAssembler is augmented to handle branches to targets
that
may exceed the immediate range of instructions.
When branching backward to a label exceeding the instruction range, the
MacroAssembler can simply tweak the generated code to use an unconditional
branch with a longer range. For example instead of
B(cond, &label);
the MacroAssembler can generate:
b(InvertCondition(cond), &done);
b(&label);
bind(&done);
Since the target is not known when the branch is emitted, forward branches
uses
a different mechanism. The MacroAssembler keeps track of forward branches to
unbound labels. When the code generation approaches the end of the range of
a
branch, a veneer is generated for the branch.
BUG=3148
Please review this at https://codereview.chromium.org/168583009/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+757, -66 lines):
src/a64/assembler-a64-inl.h
src/a64/assembler-a64.h
src/a64/assembler-a64.cc
src/a64/instructions-a64.h
src/a64/instructions-a64.cc
src/a64/macro-assembler-a64-inl.h
src/a64/macro-assembler-a64.h
src/a64/macro-assembler-a64.cc
test/cctest/test-assembler-a64.cc
test/mjsunit/mjsunit.status
test/mozilla/mozilla.status
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