ARM: Improve String.getCharsNoCheck intrinsic.
- Optimize for short retrievals.
- Improve performance of longer retrievals with unrolled LDR/STR.
Change-Id: I24ec52067104b2f68799c04aebb61d20fff94020
diff --git a/compiler/optimizing/intrinsics_arm.cc b/compiler/optimizing/intrinsics_arm.cc
index 29f7672..7d1c2eb 100644
--- a/compiler/optimizing/intrinsics_arm.cc
+++ b/compiler/optimizing/intrinsics_arm.cc
@@ -2031,7 +2031,7 @@
locations->SetInAt(3, Location::RequiresRegister());
locations->SetInAt(4, Location::RequiresRegister());
- locations->AddTemp(Location::RequiresRegister());
+ // Temporary registers to store lengths of strings and for calculations.
locations->AddTemp(Location::RequiresRegister());
locations->AddTemp(Location::RequiresRegister());
locations->AddTemp(Location::RequiresRegister());
@@ -2059,28 +2059,55 @@
Register dstObj = locations->InAt(3).AsRegister<Register>();
Register dstBegin = locations->InAt(4).AsRegister<Register>();
- Register src_ptr = locations->GetTemp(0).AsRegister<Register>();
- Register src_ptr_end = locations->GetTemp(1).AsRegister<Register>();
+ Register num_chr = locations->GetTemp(0).AsRegister<Register>();
+ Register src_ptr = locations->GetTemp(1).AsRegister<Register>();
Register dst_ptr = locations->GetTemp(2).AsRegister<Register>();
- Register tmp = locations->GetTemp(3).AsRegister<Register>();
// src range to copy.
__ add(src_ptr, srcObj, ShifterOperand(value_offset));
- __ add(src_ptr_end, src_ptr, ShifterOperand(srcEnd, LSL, 1));
__ add(src_ptr, src_ptr, ShifterOperand(srcBegin, LSL, 1));
// dst to be copied.
__ add(dst_ptr, dstObj, ShifterOperand(data_offset));
__ add(dst_ptr, dst_ptr, ShifterOperand(dstBegin, LSL, 1));
+ __ subs(num_chr, srcEnd, ShifterOperand(srcBegin));
+
// Do the copy.
- Label loop, done;
- __ Bind(&loop);
- __ cmp(src_ptr, ShifterOperand(src_ptr_end));
+ Label loop, remainder, done;
+
+ // Early out for valid zero-length retrievals.
__ b(&done, EQ);
- __ ldrh(tmp, Address(src_ptr, char_size, Address::PostIndex));
- __ strh(tmp, Address(dst_ptr, char_size, Address::PostIndex));
- __ b(&loop);
+
+ // Save repairing the value of num_chr on the < 4 character path.
+ __ subs(IP, num_chr, ShifterOperand(4));
+ __ b(&remainder, LT);
+
+ // Keep the result of the earlier subs, we are going to fetch at least 4 characters.
+ __ mov(num_chr, ShifterOperand(IP));
+
+ // Main loop used for longer fetches loads and stores 4x16-bit characters at a time.
+ // (LDRD/STRD fault on unaligned addresses and it's not worth inlining extra code
+ // to rectify these everywhere this intrinsic applies.)
+ __ Bind(&loop);
+ __ ldr(IP, Address(src_ptr, char_size * 2));
+ __ subs(num_chr, num_chr, ShifterOperand(4));
+ __ str(IP, Address(dst_ptr, char_size * 2));
+ __ ldr(IP, Address(src_ptr, char_size * 4, Address::PostIndex));
+ __ str(IP, Address(dst_ptr, char_size * 4, Address::PostIndex));
+ __ b(&loop, GE);
+
+ __ adds(num_chr, num_chr, ShifterOperand(4));
+ __ b(&done, EQ);
+
+ // Main loop for < 4 character case and remainder handling. Loads and stores one
+ // 16-bit Java character at a time.
+ __ Bind(&remainder);
+ __ ldrh(IP, Address(src_ptr, char_size, Address::PostIndex));
+ __ subs(num_chr, num_chr, ShifterOperand(1));
+ __ strh(IP, Address(dst_ptr, char_size, Address::PostIndex));
+ __ b(&remainder, GT);
+
__ Bind(&done);
}
