Is there an existing CVA6 bug for this?

• I have searched the existing bug issues

Bug Description

Issue Overview

• In the CVA6 execution reports, mixed float/integer instructions such as flt.h and fcvt.wu.h are logged as if they wrote to the floating-point destination, even though they actually write to an integer register.
• The core still updates the correct integer register; subsequent integer instructions observe the new value, but the trace attributes the write to the wrong register file.

Reproduction Steps

1. Use the two minimal assembly snippets listed below (Scenario A and Scenario B).
2. Inspect the tail of each log, locate the flt.h and fcvt.wu.h entries, and compare them with the descriptions in this report.

Expected vs. Observed

• Expected: The trace should report an update to the integer destination register (x23, x21, …) with the correct value.
• Observed: The trace instead shows the corresponding floating-point register (f23, f21, …) being updated while the integer register retains its stale value in the log.

Evidence

• Scenario A’s trace line for flt.h x23, f17, f19 states that f23 was written with 0x0, and makes no mention of x23.

• The next line, addi x19, x23, 0, sets x19 = 0, proving that x23 actually received the new value despite the missing log entry.

• Scenario B reports fcvt.wu.h x21, f18, dyn as writing f21 = 0xffffffffffffffff, again ignoring x21.

• The subsequent addi x19, x21, 0 writes x19 = 0xffffffffffffffff, confirming that the integer register was updated while the trace misattributes the writeback.

• Scenario A’s log line states “flt.h x23, f17, f19 → f23=0x0,” and the next line “addi x19, x23, 0” records x19 = 0.

• Scenario B’s log line states “fcvt.wu.h x21, f18, dyn → f21=0xffffffffffffffff,” followed immediately by “addi x19, x21, 0” recording x19 = 0xffffffffffffffff.

Instruction Snippets

Scenario A

li x2, 0xfff0000000000000
fmv.d.x f17, x2
li x2, 0xffffffffffff7e00
fmv.d.x f19, x2
li x23, 0xfffffffe
li x19, 0x0
flt.h x23, f17, f19
addi x19, x23, 0

got

core   0: 0x00000000800008c4 (0xa5389bd3) DASM(a5389bd3)
3 0x00000000800008c4 (0xa5389bd3) f23 0x0000000000000000
core   0: 0x00000000800008c8 (0x000089de) DASM(000089de)
3 0x00000000800008c8 (0x89de) x19 0x0000000000000000

Scenario B

li x2, 0xadf4a72d3abbcacf
fmv.d.x f18, x2
li x21, 0x0
li x19, 0x0
fcvt.wu.h x21, f18, dyn
addi x19, x21, 0

got

core   0: 0x00000000800008a8 (0xc4197ad3) DASM(c4197ad3)
3 0x00000000800008a8 (0xc4197ad3) f21 0xffffffffffffffff
core   0: 0x00000000800008ac (0x000089d6) DASM(000089d6)
3 0x00000000800008ac (0x89d6) x19 0xffffffffffffffff