cmd/5a, cmd/dist, runtime: support m/g in the assembler, drop support for R9/R10

to avoid unintentionally clobber R9/R10.
Thanks Lucio for the suggestion.

PS: yes, this could be considered a big change (but not an API change), but
as it turns out even temporarily changes R9/R10 in user code is unsafe and
leads to very hard to diagnose problems later, better to disable using R9/R10
when the user first uses it.
See CL 6300043 and CL 6305100 for two problems caused by misusing R9/R10.

R=golang-dev, khr, rsc
CC=golang-dev
https://golang.org/cl/9840043

diff --git a/doc/go1.2.txt b/doc/go1.2.txt
index 01b98bec4cdaea3e25380c4f45b9b012758ffa17..fd09d6a467bf0d7ef58aed761943322db3594a12 100644 (file)
--- a/doc/go1.2.txt
+++ b/doc/go1.2.txt
@@ -8,5 +8,7 @@ Please keep the descriptions to a single line, starting with the
 package or cmd/xxx directory name, and ending in a CL number.
 Please keep the list sorted (as in sort.Strings of the lines).
 
+cmd/5a: removed support for R9/R10 (use m/g instead) (CL 9840043).
+
 fmt: indexed access to arguments in Printf etc. (CL 9680043).
 io: Copy prioritizes WriterTo over ReaderFrom (CL 9462044).

diff --git a/src/cmd/5a/lex.c b/src/cmd/5a/lex.c
index a77e3050dc6a47ad5bc75f64c6323e06867b642e..3ce1bfe9524ba04b36b456577aa12add1f76d65e 100644 (file)
--- a/src/cmd/5a/lex.c
+++ b/src/cmd/5a/lex.c
@@ -191,8 +191,8 @@ struct
        "R6",           LREG,   6,
        "R7",           LREG,   7,
        "R8",           LREG,   8,
-       "R9",           LREG,   9,
-       "R10",          LREG,   10,
+       "m",            LREG,   9, // avoid unintentionally clobber m/g using R9/R10
+       "g",            LREG,   10,
        "R11",          LREG,   11,
        "R12",          LREG,   12,
        "R13",          LREG,   13,

diff --git a/src/cmd/dist/buildruntime.c b/src/cmd/dist/buildruntime.c
index ee867566fb4eb5022186a43491f32e3f297b6aa4..8f3fc541633c847ec8b4e287be92a13a0775f792 100644 (file)
--- a/src/cmd/dist/buildruntime.c
+++ b/src/cmd/dist/buildruntime.c
@@ -174,8 +174,6 @@ static struct {
        },
        
        {"arm", "",
-       "#define        g       R10\n"
-       "#define        m       R9\n"
        "#define        LR      R14\n"
        },
 };

diff --git a/src/pkg/runtime/cgo/asm_arm.s b/src/pkg/runtime/cgo/asm_arm.s
index a6ea0dc0781d0c24e05acd2af1c9f640d40e1819..e37c506c4110118393fa7cf2717359f95f264c52 100644 (file)
--- a/src/pkg/runtime/cgo/asm_arm.s
+++ b/src/pkg/runtime/cgo/asm_arm.s
@@ -15,9 +15,9 @@ TEXT crosscall2(SB),7,$-4
         *  Additionally, cgo_tls_set_gm will clobber R0, so we need to save R0
         *  nevertheless.
         */
-       MOVM.WP [R0, R1, R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, R14], (R13)
+       MOVM.WP [R0, R1, R2, R4, R5, R6, R7, R8, m, g, R11, R12, R14], (R13)
        MOVW    _cgo_load_gm(SB), R0
        BL      (R0)
        MOVW    PC, R14
        MOVW    0(R13), PC
-       MOVM.IAW        (R13), [R0, R1, R2, R4, R5, R6, R7, R8, R9, R10, R11, R12, PC]
+       MOVM.IAW        (R13), [R0, R1, R2, R4, R5, R6, R7, R8, m, g, R11, R12, PC]

diff --git a/src/pkg/runtime/vlop_arm.s b/src/pkg/runtime/vlop_arm.s
index 0dedc316a78cca759bf13781862719dd9d31ef5a..3a9cac9448e1ba7cc7c8db3df1d7f0ec8ab7d828 100644 (file)
--- a/src/pkg/runtime/vlop_arm.s
+++ b/src/pkg/runtime/vlop_arm.s
@@ -70,7 +70,7 @@ TEXT _sfloat(SB), 7, $64 // 4 arg + 14*4 saved regs + cpsr
 q = 0 // input d, output q
 r = 1 // input n, output r
 s = 2 // three temporary variables
-m = 3
+M = 3
 a = 11
 // Please be careful when changing this, it is pretty fragile:
 // 1, don't use unconditional branch as the linker is free to reorder the blocks;
@@ -83,31 +83,31 @@ TEXT udiv<>(SB),7,$-4
 
 begin:
        SUB.S   $7, R(s)
-       RSB     $0, R(q), R(m) // m = -q
+       RSB     $0, R(q), R(M) // M = -q
        MOVW.PL R(a)<<R(s), R(q)
 
        // 1st Newton iteration
-       MUL.PL  R(m), R(q), R(a) // a = -q*d
+       MUL.PL  R(M), R(q), R(a) // a = -q*d
        BMI     udiv_by_large_d
        MULAWT  R(a), R(q), R(q), R(q) // q approx q-(q*q*d>>32)
-       TEQ     R(m)->1, R(m) // check for d=0 or d=1
+       TEQ     R(M)->1, R(M) // check for d=0 or d=1
 
        // 2nd Newton iteration
-       MUL.NE  R(m), R(q), R(a)
+       MUL.NE  R(M), R(q), R(a)
        MOVW.NE $0, R(s)
        MULAL.NE R(q), R(a), (R(q),R(s))
        BEQ     udiv_by_0_or_1
 
        // q now accurate enough for a remainder r, 0<=r<3*d
        MULLU   R(q), R(r), (R(q),R(s)) // q = (r * q) >> 32    
-       ADD     R(m), R(r), R(r) // r = n - d
-       MULA    R(m), R(q), R(r), R(r) // r = n - (q+1)*d
+       ADD     R(M), R(r), R(r) // r = n - d
+       MULA    R(M), R(q), R(r), R(r) // r = n - (q+1)*d
 
        // since 0 <= n-q*d < 3*d; thus -d <= r < 2*d
-       CMN     R(m), R(r) // t = r-d
-       SUB.CS  R(m), R(r), R(r) // if (t<-d || t>=0) r=r+d
+       CMN     R(M), R(r) // t = r-d
+       SUB.CS  R(M), R(r), R(r) // if (t<-d || t>=0) r=r+d
        ADD.CC  $1, R(q)
-       ADD.PL  R(m)<<1, R(r)
+       ADD.PL  R(M)<<1, R(r)
        ADD.PL  $2, R(q)
 
        // return, can't use RET here or fast_udiv_tab will be dropped during linking
@@ -119,14 +119,14 @@ udiv_by_large_d:
        RSB     $0, R(s), R(s)
        MOVW    R(a)>>R(s), R(q)
        MULLU   R(q), R(r), (R(q),R(s))
-       MULA    R(m), R(q), R(r), R(r)
+       MULA    R(M), R(q), R(r), R(r)
 
        // q now accurate enough for a remainder r, 0<=r<4*d
-       CMN     R(r)>>1, R(m) // if(r/2 >= d)
-       ADD.CS  R(m)<<1, R(r)
+       CMN     R(r)>>1, R(M) // if(r/2 >= d)
+       ADD.CS  R(M)<<1, R(r)
        ADD.CS  $2, R(q)
-       CMN     R(r), R(m)
-       ADD.CS  R(m), R(r)
+       CMN     R(r), R(M)
+       ADD.CS  R(M), R(r)
        ADD.CS  $1, R(q)
 
        // return, can't use RET here or fast_udiv_tab will be dropped during linking
@@ -170,7 +170,7 @@ TEXT _divu(SB), 7, $16
        MOVW    R(q), 4(R13)
        MOVW    R(r), 8(R13)
        MOVW    R(s), 12(R13)
-       MOVW    R(m), 16(R13)
+       MOVW    R(M), 16(R13)
 
        MOVW    R(TMP), R(r)            /* numerator */
        MOVW    0(FP), R(q)             /* denominator */
@@ -179,14 +179,14 @@ TEXT _divu(SB), 7, $16
        MOVW    4(R13), R(q)
        MOVW    8(R13), R(r)
        MOVW    12(R13), R(s)
-       MOVW    16(R13), R(m)
+       MOVW    16(R13), R(M)
        RET
 
 TEXT _modu(SB), 7, $16
        MOVW    R(q), 4(R13)
        MOVW    R(r), 8(R13)
        MOVW    R(s), 12(R13)
-       MOVW    R(m), 16(R13)
+       MOVW    R(M), 16(R13)
 
        MOVW    R(TMP), R(r)            /* numerator */
        MOVW    0(FP), R(q)             /* denominator */
@@ -195,14 +195,14 @@ TEXT _modu(SB), 7, $16
        MOVW    4(R13), R(q)
        MOVW    8(R13), R(r)
        MOVW    12(R13), R(s)
-       MOVW    16(R13), R(m)
+       MOVW    16(R13), R(M)
        RET
 
 TEXT _div(SB),7,$16
        MOVW    R(q), 4(R13)
        MOVW    R(r), 8(R13)
        MOVW    R(s), 12(R13)
-       MOVW    R(m), 16(R13)
+       MOVW    R(M), 16(R13)
        MOVW    R(TMP), R(r)            /* numerator */
        MOVW    0(FP), R(q)             /* denominator */
        CMP     $0, R(r)
@@ -228,7 +228,7 @@ TEXT _mod(SB),7,$16
        MOVW    R(q), 4(R13)
        MOVW    R(r), 8(R13)
        MOVW    R(s), 12(R13)
-       MOVW    R(m), 16(R13)
+       MOVW    R(M), 16(R13)
        MOVW    R(TMP), R(r)            /* numerator */
        MOVW    0(FP), R(q)             /* denominator */
        CMP     $0, R(q)
@@ -246,5 +246,5 @@ out:
        MOVW    4(R13), R(q)
        MOVW    8(R13), R(r)
        MOVW    12(R13), R(s)
-       MOVW    16(R13), R(m)
+       MOVW    16(R13), R(M)
        RET