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=v8:3148
LOG=Y
R=ulan@chromium.org
Review URL: https://codereview.chromium.org/169893002
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19444 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This addresses several TODOs:
- Push and Pop requests can be queued up so that arrays of Registers
can be pushed efficiently, with just one PrepareForPush/Pop.
- PushMultipleTimes now takes an Operand. This allows variable-length
arguments arrays to be initialized, for example.
- A NoUseRealAbortsScope has been added to Abort so that
AssertStackConsistency can be called from PrepareForPush without
introducing infinite recursion.
BUG=
R=ulan@chromium.org
Review URL: https://codereview.chromium.org/169533002
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19403 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
