Bug#1144887: golang-1.26: FTBFS on riscv64: FAIL: TestMergeLocalsIntegration

Source: golang-1.26
Version: 1.26.6-2
Severity: serious
Tags: ftbfs upstream patch
Justification: fails to build from source (but built successfully in the past)
X-Debbugs-Cc: [email protected]
User: [email protected]
Usertags: riscv64

Dear maintainer,

golang-1.26 fails to build on riscv64 with an error in the testsuite:

| ?   	cmd/compile/internal/staticinit	[no test files]
| ok  	cmd/compile/internal/syntax	0.398s
| --- FAIL: TestMergeLocalsIntegration (0.52s)
|     mergelocals_test.go:181: =-= raw cand list for func ABC:
|          0: integration.go:65:6 "p1" sz=8200 hp=true align=8 t=Pointery
|          1: integration.go:65:10 "p2" sz=8200 hp=true align=8 t=Pointery
|          2: integration.go:71:7 "xp3" sz=8200 hp=true align=8 t=Pointery2
|          3: integration.go:82:7 "xp4" sz=8200 hp=true align=8 t=Pointery2
|          4: integration.go:48:7 "v2" sz=8200 hp=false align=8 t=Vanilla
|          5: integration.go:53:7 "v3" sz=8200 hp=false align=8 t=Vanilla2
|          6: integration.go:60:6 "s" sz=8192 hp=false align=8 t=Single
|         =-= addregion st=0 en=6: add part 0 -> 6
|         
|     mergelocals_test.go:182: expected trace output on 8 vars got 0
| CODE:

The full build log is available there:
https://buildd.debian.org/status/fetch.php?pkg=golang-1.26&arch=riscv64&ver=1.26.6-2&stamp=1787146614&raw=0

The issue is perfectly reproductible, and does not happened with
golang-1.27. Therefore I looked for and upstream fix, and I have found
that commit which needs to be backported:
https://github.com/golang/go/commit/5d5c7ff1f012bb70d653c1a2b282ee46161b6914

A proposed backport for the 1.26 branch is available here:
https://go-review.googlesource.com/c/go/+/812900/2

With it the testsuite passes on riscv64.

Regards
Aurelien