runtime, math/big: allow R0 on s390x to contain values other than 0

The new SSA backend for s390x can use R0 as a general purpose register.
This change modifies assembly code to either avoid using R0 entirely
or explicitly set R0 to 0.

R0 can still be safely used as 0 in address calculations.

Change-Id: I3efa723e9ef322a91a408bd8c31768d7858526c8
Reviewed-on: https://go-review.googlesource.com/28976
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/math/big/arith_s390x.s b/src/math/big/arith_s390x.s
index a691970810d05c7b2dcf4241c27601e8fb81fcd0..21929c169f93f9cb23a769aae2d8ea3f90470ac7 100644 (file)
--- a/src/math/big/arith_s390x.s
+++ b/src/math/big/arith_s390x.s
@@ -271,6 +271,7 @@ E4: MOVD R4, c+56(FP)       // return c
 // func shlVU(z, x []Word, s uint) (c Word)
 TEXT ·shlVU(SB),NOSPLIT,$0
        MOVD z_len+8(FP), R5
+       MOVD $0, R0
        SUB  $1, R5             // n--
        BLT  X8b                // n < 0        (n <= 0)
 
@@ -358,6 +359,7 @@ E864:       CMPBGT R5, R0, L864     // i < n-1
 // func shrVU(z, x []Word, s uint) (c Word)
 TEXT ·shrVU(SB),NOSPLIT,$0
        MOVD z_len+8(FP), R5
+       MOVD $0, R0
        SUB  $1, R5             // n--
        BLT  X9b                // n < 0        (n <= 0)
 

diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 928fe37121686f5077fcc15a1e5727937d4a45d9..3fe224df37a136fb45c7668a22bafb846f1175a2 100644 (file)
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -110,22 +110,22 @@ nocgo:
        MOVD    $runtime·mainPC(SB), R2                // entry
        SUB     $24, R15
        MOVD    R2, 16(R15)
-       MOVD    R0, 8(R15)
-       MOVD    R0, 0(R15)
+       MOVD    $0, 8(R15)
+       MOVD    $0, 0(R15)
        BL      runtime·newproc(SB)
        ADD     $24, R15
 
        // start this M
        BL      runtime·mstart(SB)
 
-       MOVD    R0, 1(R0)
+       MOVD    $0, 1(R0)
        RET
 
 DATA   runtime·mainPC+0(SB)/8,$runtime·main(SB)
 GLOBL  runtime·mainPC(SB),RODATA,$8
 
 TEXT runtime·breakpoint(SB),NOSPLIT|NOFRAME,$0-0
-       MOVD    R0, 2(R0)
+       MOVD    $0, 2(R0)
        RET
 
 TEXT runtime·asminit(SB),NOSPLIT|NOFRAME,$0-0
@@ -175,7 +175,7 @@ TEXT runtime·mcall(SB), NOSPLIT, $-8-8
        // Save caller state in g->sched
        MOVD    R15, (g_sched+gobuf_sp)(g)
        MOVD    LR, (g_sched+gobuf_pc)(g)
-       MOVD    R0, (g_sched+gobuf_lr)(g)
+       MOVD    $0, (g_sched+gobuf_lr)(g)
        MOVD    g, (g_sched+gobuf_g)(g)
 
        // Switch to m->g0 & its stack, call fn.
@@ -232,7 +232,7 @@ switch:
        ADD     $16, R6 // get past prologue
        MOVD    R6, (g_sched+gobuf_pc)(g)
        MOVD    R15, (g_sched+gobuf_sp)(g)
-       MOVD    R0, (g_sched+gobuf_lr)(g)
+       MOVD    $0, (g_sched+gobuf_lr)(g)
        MOVD    g, (g_sched+gobuf_g)(g)
 
        // switch to g0
@@ -526,7 +526,7 @@ g0:
        MOVD    (g_stack+stack_hi)(R5), R5
        SUB     R2, R5
        MOVD    R5, 160(R15)             // save depth in old g stack (can't just save SP, as stack might be copied during a callback)
-       MOVD    R0, 0(R15)              // clear back chain pointer (TODO can we give it real back trace information?)
+       MOVD    $0, 0(R15)              // clear back chain pointer (TODO can we give it real back trace information?)
        MOVD    R4, R2                  // arg in R2
        BL      R3                      // can clobber: R0-R5, R14, F0-F3, F5, F7-F15
 

diff --git a/src/runtime/memclr_s390x.s b/src/runtime/memclr_s390x.s
index 86eafec0a900358e378869e50ac36ee05a6595e3..846131e9f5b4ff1884a4c149bd175312fe1c77d4 100644 (file)
--- a/src/runtime/memclr_s390x.s
+++ b/src/runtime/memclr_s390x.s
@@ -16,8 +16,8 @@ start:
        CMPBLE  R5, $15, clear12to15
        CMP     R5, $32
        BGE     clearmt32
-       MOVD    R0, 0(R4)
-       MOVD    R0, 8(R4)
+       MOVD    $0, 0(R4)
+       MOVD    $0, 8(R4)
        ADD     $16, R4
        SUB     $16, R5
        BR      start
@@ -25,79 +25,79 @@ start:
 clear0to3:
        CMPBEQ  R5, $0, done
        CMPBNE  R5, $1, clear2
-       MOVB    R0, 0(R4)
+       MOVB    $0, 0(R4)
        RET
 clear2:
        CMPBNE  R5, $2, clear3
-       MOVH    R0, 0(R4)
+       MOVH    $0, 0(R4)
        RET
 clear3:
-       MOVH    R0, 0(R4)
-       MOVB    R0, 2(R4)
+       MOVH    $0, 0(R4)
+       MOVB    $0, 2(R4)
        RET
 
 clear4to7:
        CMPBNE  R5, $4, clear5
-       MOVW    R0, 0(R4)
+       MOVW    $0, 0(R4)
        RET
 clear5:
        CMPBNE  R5, $5, clear6
-       MOVW    R0, 0(R4)
-       MOVB    R0, 4(R4)
+       MOVW    $0, 0(R4)
+       MOVB    $0, 4(R4)
        RET
 clear6:
        CMPBNE  R5, $6, clear7
-       MOVW    R0, 0(R4)
-       MOVH    R0, 4(R4)
+       MOVW    $0, 0(R4)
+       MOVH    $0, 4(R4)
        RET
 clear7:
-       MOVW    R0, 0(R4)
-       MOVH    R0, 4(R4)
-       MOVB    R0, 6(R4)
+       MOVW    $0, 0(R4)
+       MOVH    $0, 4(R4)
+       MOVB    $0, 6(R4)
        RET
 
 clear8to11:
        CMPBNE  R5, $8, clear9
-       MOVD    R0, 0(R4)
+       MOVD    $0, 0(R4)
        RET
 clear9:
        CMPBNE  R5, $9, clear10
-       MOVD    R0, 0(R4)
-       MOVB    R0, 8(R4)
+       MOVD    $0, 0(R4)
+       MOVB    $0, 8(R4)
        RET
 clear10:
        CMPBNE  R5, $10, clear11
-       MOVD    R0, 0(R4)
-       MOVH    R0, 8(R4)
+       MOVD    $0, 0(R4)
+       MOVH    $0, 8(R4)
        RET
 clear11:
-       MOVD    R0, 0(R4)
-       MOVH    R0, 8(R4)
-       MOVB    R0, 10(R4)
+       MOVD    $0, 0(R4)
+       MOVH    $0, 8(R4)
+       MOVB    $0, 10(R4)
        RET
 
 clear12to15:
        CMPBNE  R5, $12, clear13
-       MOVD    R0, 0(R4)
-       MOVW    R0, 8(R4)
+       MOVD    $0, 0(R4)
+       MOVW    $0, 8(R4)
        RET
 clear13:
        CMPBNE  R5, $13, clear14
-       MOVD    R0, 0(R4)
-       MOVW    R0, 8(R4)
-       MOVB    R0, 12(R4)
+       MOVD    $0, 0(R4)
+       MOVW    $0, 8(R4)
+       MOVB    $0, 12(R4)
        RET
 clear14:
        CMPBNE  R5, $14, clear15
-       MOVD    R0, 0(R4)
-       MOVW    R0, 8(R4)
-       MOVH    R0, 12(R4)
+       MOVD    $0, 0(R4)
+       MOVW    $0, 8(R4)
+       MOVH    $0, 12(R4)
        RET
 clear15:
-       MOVD    R0, 0(R4)
-       MOVW    R0, 8(R4)
-       MOVH    R0, 12(R4)
-       MOVB    R0, 14(R4)
+       MOVD    $0, 0(R4)
+       MOVW    $0, 8(R4)
+       MOVH    $0, 12(R4)
+       MOVB    $0, 14(R4)
        RET
 
 clearmt32:
@@ -117,6 +117,6 @@ done:
 // DO NOT CALL - target for exrl (execute relative long) instruction.
 TEXT runtime·memclr_s390x_exrl_xc(SB),NOSPLIT|NOFRAME,$0-0
        XC      $1, 0(R4), 0(R4)
-       MOVD    R0, 0(R0)
+       MOVD    $0, 0(R0)
        RET