From d186d07eda6cb043c4c75ef6ec3e161e7f6c5a3e Mon Sep 17 00:00:00 2001
From: Shenghou Ma <minux.ma@gmail.com>
Date: Sun, 3 Jun 2012 03:08:49 +0800
Subject: [PATCH] cmd/5a, cmd/5l, math: add CLZ instruction for ARM        
 Supported in ARMv5 and above.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6284043
---
 src/cmd/5a/lex.c             | 2 ++
 src/cmd/5l/5.out.h           | 4 +++-
 src/cmd/5l/asm.c             | 9 +++++++++
 src/cmd/5l/optab.c           | 2 ++
 src/cmd/5l/span.c            | 1 +
 src/pkg/math/big/arith_arm.s | 2 +-
 6 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/cmd/5a/lex.c b/src/cmd/5a/lex.c
index e569fe62d3a..6064becb9f0 100644
--- a/src/cmd/5a/lex.c
+++ b/src/cmd/5a/lex.c
@@ -406,6 +406,8 @@ struct
 
 	"PLD",		LTYPEPLD, APLD,
 	"UNDEF",	LTYPEE,	AUNDEF,
+	"CLZ",		LTYPE2, ACLZ,
+
 	0
 };
 
diff --git a/src/cmd/5l/5.out.h b/src/cmd/5l/5.out.h
index 56724d3dbce..df5b5186a2c 100644
--- a/src/cmd/5l/5.out.h
+++ b/src/cmd/5l/5.out.h
@@ -184,9 +184,11 @@ enum	as
 	ASTREXD,
 
 	APLD,
-	
+
 	AUNDEF,
 
+	ACLZ,
+
 	ALAST,
 };
 
diff --git a/src/cmd/5l/asm.c b/src/cmd/5l/asm.c
index 6d9d0b3f210..d8fde468322 100644
--- a/src/cmd/5l/asm.c
+++ b/src/cmd/5l/asm.c
@@ -1801,6 +1801,11 @@ if(debug['G']) print("%ux: %s: arm %d\n", (uint32)(p->pc), p->from.sym->name, p-
 		o1 = opbra(ABL, C_SCOND_NONE);
 		o1 |= (v >> 2) & 0xffffff;
 		break;
+	case 97:	/* CLZ Rm, Rd */
+ 		o1 = oprrr(p->as, p->scond);
+ 		o1 |= p->to.reg << 12;
+ 		o1 |= p->from.reg;
+		break;
 	}
 	
 	out[0] = o1;
@@ -1958,6 +1963,10 @@ oprrr(int a, int sc)
 		return o | (0xe<<24) | (0x1<<20) | (0xb<<8) | (1<<4);
 	case ACMP+AEND:	// cmp imm
 		return o | (0x3<<24) | (0x5<<20);
+
+	case ACLZ:
+		// CLZ doesn't support .S
+		return (o & (0xf<<28)) | (0x16f<<16) | (0xf1<<4);
 	}
 	diag("bad rrr %d", a);
 	prasm(curp);
diff --git a/src/cmd/5l/optab.c b/src/cmd/5l/optab.c
index be25b6ed611..9edbec09d67 100644
--- a/src/cmd/5l/optab.c
+++ b/src/cmd/5l/optab.c
@@ -236,5 +236,7 @@ Optab	optab[] =
 	
 	{ AUNDEF,		C_NONE,	C_NONE,	C_NONE,		96, 4, 0 },
 
+	{ ACLZ,		C_REG,	C_NONE,	C_REG,		97, 4, 0 },
+
 	{ AXXX,		C_NONE,	C_NONE,	C_NONE,		 0, 4, 0 },
 };
diff --git a/src/cmd/5l/span.c b/src/cmd/5l/span.c
index acacb66bb06..bda4981ee1d 100644
--- a/src/cmd/5l/span.c
+++ b/src/cmd/5l/span.c
@@ -848,6 +848,7 @@ buildop(void)
 		case ATST:
 		case APLD:
 		case AUNDEF:
+		case ACLZ:
 			break;
 		}
 	}
diff --git a/src/pkg/math/big/arith_arm.s b/src/pkg/math/big/arith_arm.s
index dbf3360b58e..ed0f371655e 100644
--- a/src/pkg/math/big/arith_arm.s
+++ b/src/pkg/math/big/arith_arm.s
@@ -314,7 +314,7 @@ TEXT ·mulWW(SB),7,$0
 // func bitLen(x Word) (n int)
 TEXT ·bitLen(SB),7,$0
 	MOVW	x+0(FP), R0
-	WORD	$0xe16f0f10 // CLZ R0, R0  (count leading zeros)
+	CLZ 	R0, R0
 	MOVW	$32, R1
 	SUB.S	R0, R1
 	MOVW	R1, n+4(FP)