[optimizing] Improve x86 parallel moves/swaps
Add a new constructor to ScratchRegisterScope that will supply a
register if there is a free one, but not spill to force one. Use this
to generated alternate code that doesn't use a temporary, as the
spill/restore of a register generates extra instructions that aren't
necessary on x86.
Here is the benefit for a 32 bit memory-to-memory exchange with no
free registers:
< 50 push eax
< 53 push ebx
< 8B44244C mov eax, [esp + 76]
< 8B5C246C mov ebx, [esp + 108]
< 8944246C mov [esp + 108], eax
< 895C244C mov [esp + 76], ebx
< 5B pop ebx
< 58 pop eax
---
> FF742444 push [esp + 68]
> FF742468 push [esp + 104]
> 8F44244C pop [esp + 72]
> 8F442468 pop [esp + 100]
Avoid using xchg instruction, as it is slow on smaller processors.
Change-Id: Id29ee3abd998577baaee552d55d23e60ae0c7871
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 4d74683..183453d 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -3958,23 +3958,43 @@
}
void ParallelMoveResolverX86::MoveMemoryToMemory32(int dst, int src) {
- ScratchRegisterScope ensure_scratch(
- this, kNoRegister, EAX, codegen_->GetNumberOfCoreRegisters());
- Register temp_reg = static_cast<Register>(ensure_scratch.GetRegister());
- int stack_offset = ensure_scratch.IsSpilled() ? kX86WordSize : 0;
- __ movl(temp_reg, Address(ESP, src + stack_offset));
- __ movl(Address(ESP, dst + stack_offset), temp_reg);
+ ScratchRegisterScope possible_scratch(
+ this, kNoRegister, codegen_->GetNumberOfCoreRegisters());
+ int temp = possible_scratch.GetRegister();
+ if (temp == kNoRegister) {
+ // Use the stack.
+ __ pushl(Address(ESP, src));
+ __ popl(Address(ESP, dst));
+ } else {
+ Register temp_reg = static_cast<Register>(temp);
+ __ movl(temp_reg, Address(ESP, src));
+ __ movl(Address(ESP, dst), temp_reg);
+ }
}
void ParallelMoveResolverX86::MoveMemoryToMemory64(int dst, int src) {
- ScratchRegisterScope ensure_scratch(
- this, kNoRegister, EAX, codegen_->GetNumberOfCoreRegisters());
- Register temp_reg = static_cast<Register>(ensure_scratch.GetRegister());
- int stack_offset = ensure_scratch.IsSpilled() ? kX86WordSize : 0;
- __ movl(temp_reg, Address(ESP, src + stack_offset));
- __ movl(Address(ESP, dst + stack_offset), temp_reg);
- __ movl(temp_reg, Address(ESP, src + stack_offset + kX86WordSize));
- __ movl(Address(ESP, dst + stack_offset + kX86WordSize), temp_reg);
+ ScratchRegisterScope possible_scratch(
+ this, kNoRegister, codegen_->GetNumberOfCoreRegisters());
+ int temp = possible_scratch.GetRegister();
+ if (temp == kNoRegister) {
+ // Use the stack instead.
+ // Push src low word.
+ __ pushl(Address(ESP, src));
+ // Push src high word. Stack offset = 4.
+ __ pushl(Address(ESP, src + 4 /* offset */ + kX86WordSize /* high */));
+
+ // Pop into dst high word. Stack offset = 8.
+ // Pop with ESP address uses the 'after increment' value of ESP.
+ __ popl(Address(ESP, dst + 4 /* offset */ + kX86WordSize /* high */));
+ // Finally dst low word. Stack offset = 4.
+ __ popl(Address(ESP, dst));
+ } else {
+ Register temp_reg = static_cast<Register>(temp);
+ __ movl(temp_reg, Address(ESP, src));
+ __ movl(Address(ESP, dst), temp_reg);
+ __ movl(temp_reg, Address(ESP, src + kX86WordSize));
+ __ movl(Address(ESP, dst + kX86WordSize), temp_reg);
+ }
}
void ParallelMoveResolverX86::EmitMove(size_t index) {
@@ -4039,10 +4059,18 @@
__ xorps(dest, dest);
} else {
ScratchRegisterScope ensure_scratch(
- this, kNoRegister, EAX, codegen_->GetNumberOfCoreRegisters());
- Register temp = static_cast<Register>(ensure_scratch.GetRegister());
- __ movl(temp, Immediate(value));
- __ movd(dest, temp);
+ this, kNoRegister, codegen_->GetNumberOfCoreRegisters());
+ int temp_reg = ensure_scratch.GetRegister();
+ if (temp_reg == kNoRegister) {
+ // Avoid spilling/restoring a scratch register by using the stack.
+ __ pushl(Immediate(value));
+ __ movss(dest, Address(ESP, 0));
+ __ addl(ESP, Immediate(4));
+ } else {
+ Register temp = static_cast<Register>(temp_reg);
+ __ movl(temp, Immediate(value));
+ __ movd(dest, temp);
+ }
}
} else {
DCHECK(destination.IsStackSlot()) << destination;
@@ -4091,42 +4119,96 @@
}
}
-void ParallelMoveResolverX86::Exchange(Register reg, int mem) {
- Register suggested_scratch = reg == EAX ? EBX : EAX;
- ScratchRegisterScope ensure_scratch(
- this, reg, suggested_scratch, codegen_->GetNumberOfCoreRegisters());
+void ParallelMoveResolverX86::Exchange(Register reg1, Register reg2) {
+ // Prefer to avoid xchg as it isn't speedy on smaller processors.
+ ScratchRegisterScope possible_scratch(
+ this, reg1, codegen_->GetNumberOfCoreRegisters());
+ int temp_reg = possible_scratch.GetRegister();
+ if (temp_reg == kNoRegister || temp_reg == reg2) {
+ __ pushl(reg1);
+ __ movl(reg1, reg2);
+ __ popl(reg2);
+ } else {
+ Register temp = static_cast<Register>(temp_reg);
+ __ movl(temp, reg1);
+ __ movl(reg1, reg2);
+ __ movl(reg2, temp);
+ }
+}
- int stack_offset = ensure_scratch.IsSpilled() ? kX86WordSize : 0;
- __ movl(static_cast<Register>(ensure_scratch.GetRegister()), Address(ESP, mem + stack_offset));
- __ movl(Address(ESP, mem + stack_offset), reg);
- __ movl(reg, static_cast<Register>(ensure_scratch.GetRegister()));
+void ParallelMoveResolverX86::Exchange(Register reg, int mem) {
+ ScratchRegisterScope possible_scratch(
+ this, reg, codegen_->GetNumberOfCoreRegisters());
+ int temp_reg = possible_scratch.GetRegister();
+ if (temp_reg == kNoRegister) {
+ __ pushl(Address(ESP, mem));
+ __ movl(Address(ESP, mem + kX86WordSize), reg);
+ __ popl(reg);
+ } else {
+ Register temp = static_cast<Register>(temp_reg);
+ __ movl(temp, Address(ESP, mem));
+ __ movl(Address(ESP, mem), reg);
+ __ movl(reg, temp);
+ }
}
void ParallelMoveResolverX86::Exchange32(XmmRegister reg, int mem) {
- ScratchRegisterScope ensure_scratch(
- this, kNoRegister, EAX, codegen_->GetNumberOfCoreRegisters());
-
- Register temp_reg = static_cast<Register>(ensure_scratch.GetRegister());
- int stack_offset = ensure_scratch.IsSpilled() ? kX86WordSize : 0;
- __ movl(temp_reg, Address(ESP, mem + stack_offset));
- __ movss(Address(ESP, mem + stack_offset), reg);
- __ movd(reg, temp_reg);
+ ScratchRegisterScope possible_scratch(
+ this, kNoRegister, codegen_->GetNumberOfCoreRegisters());
+ int temp_reg = possible_scratch.GetRegister();
+ if (temp_reg == kNoRegister) {
+ __ pushl(Address(ESP, mem));
+ __ movss(Address(ESP, mem + kX86WordSize), reg);
+ __ movss(reg, Address(ESP, 0));
+ __ addl(ESP, Immediate(kX86WordSize));
+ } else {
+ Register temp = static_cast<Register>(temp_reg);
+ __ movl(temp, Address(ESP, mem));
+ __ movss(Address(ESP, mem), reg);
+ __ movd(reg, temp);
+ }
}
void ParallelMoveResolverX86::Exchange(int mem1, int mem2) {
- ScratchRegisterScope ensure_scratch1(
- this, kNoRegister, EAX, codegen_->GetNumberOfCoreRegisters());
+ ScratchRegisterScope possible_scratch1(
+ this, kNoRegister, codegen_->GetNumberOfCoreRegisters());
+ int temp_reg1 = possible_scratch1.GetRegister();
+ if (temp_reg1 == kNoRegister) {
+ // No free registers. Use the stack.
+ __ pushl(Address(ESP, mem1));
+ __ pushl(Address(ESP, mem2 + kX86WordSize));
+ // Pop with ESP address uses the 'after increment' value of ESP.
+ __ popl(Address(ESP, mem1 + kX86WordSize));
+ __ popl(Address(ESP, mem2));
+ } else {
+ // Got the first one. Try for a second.
+ ScratchRegisterScope possible_scratch2(
+ this, temp_reg1, codegen_->GetNumberOfCoreRegisters());
+ int temp_reg2 = possible_scratch2.GetRegister();
+ if (temp_reg2 == kNoRegister) {
+ Register temp = static_cast<Register>(temp_reg1);
+ // Bummer. Only have one free register to use.
+ // Save mem1 on the stack.
+ __ pushl(Address(ESP, mem1));
- Register suggested_scratch = ensure_scratch1.GetRegister() == EAX ? EBX : EAX;
- ScratchRegisterScope ensure_scratch2(
- this, ensure_scratch1.GetRegister(), suggested_scratch, codegen_->GetNumberOfCoreRegisters());
+ // Copy mem2 into mem1.
+ __ movl(temp, Address(ESP, mem2 + kX86WordSize));
+ __ movl(Address(ESP, mem1 + kX86WordSize), temp);
- int stack_offset = ensure_scratch1.IsSpilled() ? kX86WordSize : 0;
- stack_offset += ensure_scratch2.IsSpilled() ? kX86WordSize : 0;
- __ movl(static_cast<Register>(ensure_scratch1.GetRegister()), Address(ESP, mem1 + stack_offset));
- __ movl(static_cast<Register>(ensure_scratch2.GetRegister()), Address(ESP, mem2 + stack_offset));
- __ movl(Address(ESP, mem2 + stack_offset), static_cast<Register>(ensure_scratch1.GetRegister()));
- __ movl(Address(ESP, mem1 + stack_offset), static_cast<Register>(ensure_scratch2.GetRegister()));
+ // Now pop mem1 into mem2.
+ // Pop with ESP address uses the 'after increment' value of ESP.
+ __ popl(Address(ESP, mem2));
+ } else {
+ // Great. We have 2 registers to play with.
+ Register temp1 = static_cast<Register>(temp_reg1);
+ Register temp2 = static_cast<Register>(temp_reg2);
+ DCHECK_NE(temp1, temp2);
+ __ movl(temp1, Address(ESP, mem1));
+ __ movl(temp2, Address(ESP, mem2));
+ __ movl(Address(ESP, mem2), temp1);
+ __ movl(Address(ESP, mem1), temp2);
+ }
+ }
}
void ParallelMoveResolverX86::EmitSwap(size_t index) {
@@ -4135,7 +4217,7 @@
Location destination = move->GetDestination();
if (source.IsRegister() && destination.IsRegister()) {
- __ xchgl(destination.AsRegister<Register>(), source.AsRegister<Register>());
+ Exchange(destination.AsRegister<Register>(), source.AsRegister<Register>());
} else if (source.IsRegister() && destination.IsStackSlot()) {
Exchange(source.AsRegister<Register>(), destination.GetStackIndex());
} else if (source.IsStackSlot() && destination.IsRegister()) {