[release-branch.go1.14] cmd/internal/obj/ppc64: don't remove NOP in assembler

Previously, the assembler removed NOPs from the Prog list in
obj9.go. NOPs shouldn't be removed if they were added as
an inline mark, as described in the issue below.

Fixes #40766

Once the NOPs were left in the Prog list, some instructions
were flagged as invalid because they had an operand which was
not represented in optab. In order to preserve the previous
assembler behavior, entries were added to optab for those
operand cases. They were not flagged as errors before because
the NOP instructions were removed before the code to check the
valid opcode/operand combinations.

Change-Id: Iae5145f94459027cf458e914d7c5d6089807ccf8
Reviewed-on: https://go-review.googlesource.com/c/go/+/247842
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Paul Murphy <murp@ibm.com>
Reviewed-by: Michael Munday <mike.munday@ibm.com>
Reviewed-by: Keith Randall <khr@golang.org>
(cherry picked from commit 7d7bd5abc7f7ac901830b79496f63ce86895e262)
Reviewed-on: https://go-review.googlesource.com/c/go/+/248382
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>

diff --git a/src/cmd/internal/obj/ppc64/asm9.go b/src/cmd/internal/obj/ppc64/asm9.go
index 149604574b1c83d45784f47bf524cc69f72eddc9..0472375e48e7756bf2e5f1bae873c2becd4e3408 100644 (file)
--- a/src/cmd/internal/obj/ppc64/asm9.go
+++ b/src/cmd/internal/obj/ppc64/asm9.go
@@ -607,6 +607,9 @@ var optab = []Optab{
        {obj.APCDATA, C_LCON, C_NONE, C_NONE, C_LCON, 0, 0, 0},
        {obj.AFUNCDATA, C_SCON, C_NONE, C_NONE, C_ADDR, 0, 0, 0},
        {obj.ANOP, C_NONE, C_NONE, C_NONE, C_NONE, 0, 0, 0},
+       {obj.ANOP, C_LCON, C_NONE, C_NONE, C_NONE, 0, 0, 0}, // NOP operand variations added for #40689
+       {obj.ANOP, C_REG, C_NONE, C_NONE, C_NONE, 0, 0, 0},  // to preserve previous behavior
+       {obj.ANOP, C_FREG, C_NONE, C_NONE, C_NONE, 0, 0, 0},
        {obj.ADUFFZERO, C_NONE, C_NONE, C_NONE, C_LBRA, 11, 4, 0}, // same as ABR/ABL
        {obj.ADUFFCOPY, C_NONE, C_NONE, C_NONE, C_LBRA, 11, 4, 0}, // same as ABR/ABL
        {obj.APCALIGN, C_LCON, C_NONE, C_NONE, C_NONE, 0, 0, 0},   // align code

diff --git a/src/cmd/internal/obj/ppc64/obj9.go b/src/cmd/internal/obj/ppc64/obj9.go
index 7135488f9d14170c8700d9bcfb6b5913fde7ff8d..a2f16f2e2a643557de2d08510a3d137972591035 100644 (file)
--- a/src/cmd/internal/obj/ppc64/obj9.go
+++ b/src/cmd/internal/obj/ppc64/obj9.go
@@ -427,7 +427,6 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 
        /*
         * find leaf subroutines
-        * strip NOPs
         * expand RET
         * expand BECOME pseudo
         */
@@ -557,10 +556,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
                        q = p
                        q1 = p.Pcond
                        if q1 != nil {
-                               for q1.As == obj.ANOP {
-                                       q1 = q1.Link
-                                       p.Pcond = q1
-                               }
+                               // NOPs are not removed due to #40689.
 
                                if q1.Mark&LEAF == 0 {
                                        q1.Mark |= LABEL
@@ -587,9 +583,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
                        continue
 
                case obj.ANOP:
-                       q1 = p.Link
-                       q.Link = q1 /* q is non-nop */
-                       q1.Mark |= p.Mark
+                       // NOPs are not removed due to
+                       // #40689
                        continue
 
                default: