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[liftoff] Make RegsUnusedByParams constexpr

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After dropping support for older GCC versions, we can now assume full
c++14 constexpr support, and can hence resolve a TODO to make a
LiftoffCompiler method constexpr.

This is also a proof-of-concept to verify that this indeed works on all
bots now.

R=ahaas@chromium.org

Bug: v8:9686, v8:11384
Change-Id: I9b7da91152b0af98778312d653aebbf4236fed0d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2876850
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74407}
This commit is contained in:
Clemens Backes 2021-05-06 14:11:14 +02:00 committed by V8 LUCI CQ
parent dc7906c99e
commit d54e2bc781
2 changed files with 15 additions and 12 deletions
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6
src/wasm/baseline/liftoff-compiler.cc
View File

@ -593,8 +593,7 @@ class LiftoffCompiler {
}
}
// TODO(ahaas): Make this function constexpr once GCC allows it.
LiftoffRegList RegsUnusedByParams() {
constexpr static LiftoffRegList RegsUnusedByParams() {
LiftoffRegList regs = kGpCacheRegList;
for (auto reg : kGpParamRegisters) {
regs.clear(reg);
@ -619,8 +618,9 @@ class LiftoffCompiler {
// For reference type parameters we have to use registers that were not
// used for parameters because some reference type stack parameters may
// get processed before some value type register parameters.
static constexpr auto kRegsUnusedByParams = RegsUnusedByParams();
LiftoffRegister reg = is_reference(reg_kind)
? __ GetUnusedRegister(RegsUnusedByParams())
? __ GetUnusedRegister(kRegsUnusedByParams)
: __ GetUnusedRegister(rc, pinned);
__ LoadCallerFrameSlot(reg, -location.AsCallerFrameSlot(), reg_kind);
return reg;

21
src/wasm/baseline/liftoff-register.h
View File

@ -152,11 +152,12 @@ class LiftoffRegister {
"chosen type is small enough");
public:
explicit LiftoffRegister(Register reg) : LiftoffRegister(reg.code()) {
constexpr explicit LiftoffRegister(Register reg)
: LiftoffRegister(reg.code()) {
DCHECK_NE(0, kLiftoffAssemblerGpCacheRegs & reg.bit());
DCHECK_EQ(reg, gp());
}
explicit LiftoffRegister(DoubleRegister reg)
constexpr explicit LiftoffRegister(DoubleRegister reg)
: LiftoffRegister(kAfterMaxLiftoffGpRegCode + reg.code()) {
DCHECK_NE(0, kLiftoffAssemblerFpCacheRegs & reg.bit());
DCHECK_EQ(reg, fp());
@ -275,22 +276,22 @@ class LiftoffRegister {
return DoubleRegister::from_code((code_ & kCodeMask) + 1);
}
Register gp() const {
constexpr Register gp() const {
DCHECK(is_gp());
return Register::from_code(code_);
}
DoubleRegister fp() const {
constexpr DoubleRegister fp() const {
DCHECK(is_fp());
return DoubleRegister::from_code(code_ - kAfterMaxLiftoffGpRegCode);
}
int liftoff_code() const {
constexpr int liftoff_code() const {
STATIC_ASSERT(sizeof(int) >= sizeof(storage_t));
return static_cast<int>(code_);
}
RegClass reg_class() const {
constexpr RegClass reg_class() const {
return is_fp_pair() ? kFpRegPair
: is_gp_pair() ? kGpRegPair : is_gp() ? kGpReg : kFpReg;
}
@ -364,7 +365,7 @@ class LiftoffRegList {
return reg;
}
LiftoffRegister clear(LiftoffRegister reg) {
constexpr LiftoffRegister clear(LiftoffRegister reg) {
if (reg.is_pair()) {
regs_ &= ~(storage_t{1} << reg.low().liftoff_code());
regs_ &= ~(storage_t{1} << reg.high().liftoff_code());
@ -373,8 +374,10 @@ class LiftoffRegList {
}
return reg;
}
Register clear(Register reg) { return clear(LiftoffRegister{reg}).gp(); }
DoubleRegister clear(DoubleRegister reg) {
constexpr Register clear(Register reg) {
return clear(LiftoffRegister{reg}).gp();
}
constexpr DoubleRegister clear(DoubleRegister reg) {
return clear(LiftoffRegister{reg}).fp();
}