Reviewers: akos.palfi.imgtec, dusmil.imgtec,
Message:
Tested to not break anything under existing tests, but I can't repro the
code-age problem, so this is a swag at that. PTAL. For testing only, do not
commit.
Description:
MIPS: Avoid use of a0 as return address in jalr.
Trial fix for code-aging issue.
BUG=
Please review this at https://codereview.chromium.org/1218743010/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+14, -6 lines):
M src/mips/builtins-mips.cc
M src/mips/codegen-mips.cc
M src/mips/macro-assembler-mips.cc
Index: src/mips/builtins-mips.cc
diff --git a/src/mips/builtins-mips.cc b/src/mips/builtins-mips.cc
index
b5a67b47dc59892991d1f785619f6191d77b8631..20b19295eb94ed8e46c2deb4d9581cc54c132a1a
100644
--- a/src/mips/builtins-mips.cc
+++ b/src/mips/builtins-mips.cc
@@ -1024,9 +1024,12 @@ static void
GenerateMakeCodeYoungAgainCommon(MacroAssembler* masm) {
// internal frame to make the code faster, since we shouldn't have to do
stack
// crawls in MakeCodeYoung. This seems a bit fragile.
- // Set a0 to point to the head of the PlatformCodeAge sequence.
+ // Set a0 to point to the head of the PlatformCodeAge sequence, using
ret adr.
+ __ mov(a0, ra);
__ Subu(a0, a0,
Operand(kNoCodeAgeSequenceLength - Assembler::kInstrSize));
+ // Restore the original return address of the function
+ __ mov(ra, at);
// The following registers must be saved and restored when calling
through to
// the runtime:
@@ -1063,9 +1066,12 @@ void
Builtins::Generate_MarkCodeAsExecutedOnce(MacroAssembler* masm) {
// save/restore the registers without worrying about which of them
contain
// pointers.
- // Set a0 to point to the head of the PlatformCodeAge sequence.
+ // Set a0 to point to the head of the PlatformCodeAge sequence, using
ret adr.
+ __ mov(a0, ra);
__ Subu(a0, a0,
Operand(kNoCodeAgeSequenceLength - Assembler::kInstrSize));
+ // Restore the original return address of the function
+ __ mov(ra, at);
// The following registers must be saved and restored when calling
through to
// the runtime:
Index: src/mips/codegen-mips.cc
diff --git a/src/mips/codegen-mips.cc b/src/mips/codegen-mips.cc
index
23780d8b2597679c747b7eefa78bbcd34e4685de..956407bc578b7cc3633aa9282e0b8ba504e0dae3
100644
--- a/src/mips/codegen-mips.cc
+++ b/src/mips/codegen-mips.cc
@@ -1252,8 +1252,9 @@ void Code::PatchPlatformCodeAge(Isolate* isolate,
t9,
Operand(reinterpret_cast<uint32_t>(stub->instruction_start())),
CONSTANT_SIZE);
- patcher.masm()->nop(); // Prevent jalr to jal optimization.
- patcher.masm()->jalr(t9, a0);
+ // Save the function's original return address.
+ patcher.masm()->mov(at, ra); // This also prevents jalr->jal
optimization.
+ patcher.masm()->jalr(t9);
patcher.masm()->nop(); // Branch delay slot nop.
patcher.masm()->nop(); // Pad the empty space.
}
Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc
b/src/mips/macro-assembler-mips.cc
index
f554b0c1efc84757d5edc7bd2923272dc1522598..8ca73e60e6cc9ab26736ffd5484e3e553a441853
100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -4892,8 +4892,9 @@ void MacroAssembler::Prologue(bool code_pre_aging) {
li(t9,
Operand(reinterpret_cast<uint32_t>(stub->instruction_start())),
CONSTANT_SIZE);
- nop(); // Prevent jalr to jal optimization.
- jalr(t9, a0);
+ // Save the function's original return address.
+ mov(at, ra); // This also prevents jalr->jal optimization.
+ jalr(t9);
nop(); // Branch delay slot nop.
nop(); // Pad the empty space.
} else {
--
--
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