Commit 6da8bdd2 authored by Lynn Boger's avatar Lynn Boger Committed by David Chase

cmd/asm: recognize CR1-CR7 on ppc64x branch instructions

Some of the branch instructions (BEQ, BNE, BLT, etc.) accept
all the valid CR values as operands, but the CR register value is
not parsed and not put into the instruction, so that CR0 is always
used regardless of what was specified on the instruction.  For example
BEQ CR2,label becomes beq cr0,label.

This adds the change to the PPC64 assembler to recognize the CR value
and set the approppriate field in the instruction so the correct
CR is used.  This also adds some general comments on the branch
instruction BC and its operand values.

Fixes #17408

Change-Id: I8e956372a42846a4c09a7259e9172eaa29118e71
Reviewed-on: https://go-review.googlesource.com/30930
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: default avatarDavid Chase <drchase@google.com>
parent 442de98c
......@@ -213,6 +213,43 @@ const (
NOSCHED = 1 << 9
)
// Values for use in branch instruction BC
// BC B0,BI,label
// BO is type of branch + likely bits described below
// BI is CR value + branch type
// ex: BEQ CR2,label is BC 12,10,label
// 12 = BO_BCR
// 10 = BI_CR2 + BI_EQ
const (
BI_CR0 = 0
BI_CR1 = 4
BI_CR2 = 8
BI_CR3 = 12
BI_CR4 = 16
BI_CR5 = 20
BI_CR6 = 24
BI_CR7 = 28
BI_LT = 0
BI_GT = 1
BI_EQ = 2
BI_OVF = 3
)
// Values for the BO field. Add the branch type to
// the likely bits, if a likely setting is known.
// If branch likely or unlikely is not known, don't set it.
// e.g. branch on cr+likely = 15
const (
BO_BCTR = 16 // branch on ctr value
BO_BCR = 12 // branch on cr value
BO_BCRBCTR = 8 // branch on ctr and cr value
BO_NOTBCR = 4 // branch on not cr value
BO_UNLIKELY = 2 // value for unlikely
BO_LIKELY = 3 // value for likely
)
// Bit settings from the CR
const (
......
......@@ -2137,12 +2137,35 @@ func asmout(ctxt *obj.Link, p *obj.Prog, o *Optab, out []uint32) {
16: /* bc bo,bi,sbra */
a := 0
r := int(p.Reg)
if p.From.Type == obj.TYPE_CONST {
a = int(regoff(ctxt, &p.From))
}
r := int(p.Reg)
if r == 0 {
r = 0
} else if p.From.Type == obj.TYPE_REG {
if r != 0 {
ctxt.Diag("unexpected register setting for branch with CR: %d\n", r)
}
// BI values for the CR
switch p.From.Reg {
case REG_CR0:
r = BI_CR0
case REG_CR1:
r = BI_CR1
case REG_CR2:
r = BI_CR2
case REG_CR3:
r = BI_CR3
case REG_CR4:
r = BI_CR4
case REG_CR5:
r = BI_CR5
case REG_CR6:
r = BI_CR6
case REG_CR7:
r = BI_CR7
default:
ctxt.Diag("unrecognized register: expecting CR\n")
}
}
v := int32(0)
if p.Pcond != nil {
......
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