Revision: 9033
Author: [email protected]
Date: Mon Aug 29 01:41:39 2011
Log: Commenting register usage in MIPS.
Review URL: http://codereview.chromium.org/7775007
http://code.google.com/p/v8/source/detail?r=9033
Modified:
/branches/bleeding_edge/src/mips/assembler-mips.h
=======================================
--- /branches/bleeding_edge/src/mips/assembler-mips.h Mon Jul 18 07:46:35
2011
+++ /branches/bleeding_edge/src/mips/assembler-mips.h Mon Aug 29 01:41:39
2011
@@ -127,38 +127,38 @@
const Register no_reg = { -1 };
-const Register zero_reg = { 0 };
-const Register at = { 1 };
-const Register v0 = { 2 };
-const Register v1 = { 3 };
-const Register a0 = { 4 };
+const Register zero_reg = { 0 }; // Always zero.
+const Register at = { 1 }; // at: Reserved for synthetic instructions.
+const Register v0 = { 2 }; // v0, v1: Used when returning multiple values
+const Register v1 = { 3 }; // from subroutines.
+const Register a0 = { 4 }; // a0 - a4: Used to pass non-FP parameters.
const Register a1 = { 5 };
const Register a2 = { 6 };
const Register a3 = { 7 };
-const Register t0 = { 8 };
-const Register t1 = { 9 };
-const Register t2 = { 10 };
+const Register t0 = { 8 }; // t0 - t9: Can be used without reservation,
act
+const Register t1 = { 9 }; // as temporary registers and are allowed to
+const Register t2 = { 10 }; // be destroyed by subroutines.
const Register t3 = { 11 };
const Register t4 = { 12 };
const Register t5 = { 13 };
const Register t6 = { 14 };
const Register t7 = { 15 };
-const Register s0 = { 16 };
-const Register s1 = { 17 };
-const Register s2 = { 18 };
-const Register s3 = { 19 };
-const Register s4 = { 20 };
+const Register s0 = { 16 }; // s0 - s7: Subroutine register variables.
+const Register s1 = { 17 }; // Subroutines that write to these registers
+const Register s2 = { 18 }; // must restore their values before exiting
so
+const Register s3 = { 19 }; // that the caller can expect the values to
be
+const Register s4 = { 20 }; // preserved.
const Register s5 = { 21 };
const Register s6 = { 22 };
const Register s7 = { 23 };
const Register t8 = { 24 };
const Register t9 = { 25 };
-const Register k0 = { 26 };
-const Register k1 = { 27 };
-const Register gp = { 28 };
-const Register sp = { 29 };
-const Register s8_fp = { 30 };
-const Register ra = { 31 };
+const Register k0 = { 26 }; // k0, k1: Reserved for system calls and
+const Register k1 = { 27 }; // interrupt handlers.
+const Register gp = { 28 }; // gp: Reserved.
+const Register sp = { 29 }; // sp: Stack pointer.
+const Register s8_fp = { 30 }; // fp: Frame pointer.
+const Register ra = { 31 }; // ra: Return address pointer.
int ToNumber(Register reg);
--
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