722688 - asm_store64 LIR_std2f cannot have scratch rt == value rv

Status: RESOLVED FIXED

(Tamarin Graveyard :: Baseline JIT (CodegenLIR), defect, P1)

Description

[Felix S. Klock II [:pnkfelix, :fklock]]

if (rmask(rv) & XmmRegs) {
                 // need a scratch reg
-                Register rt = registerAllocTmp(XmmRegs);
+                Register rt = registerAllocTmp(XmmRegs & ~rmask(rv));

Comment 1

[Felix S. Klock II [:pnkfelix, :fklock]]

Attachment: proposed patch (checking now if it fixes WE bug)

Comment 2

[Edwin Smith]

This bug impacts the LIR_std2f instruction which is used to implement the ABC opcode OP_sf32 (truncate double to float then store).   In code sequences with heavy register pressure, the scratch register used could be the same as the one holding the value, which wrongly sets the stored value to zero.

Comment 3

[Tamarin Bot]

changeset: 7175:65e07c19b309
user:      Felix S Klock II <fklockii>
summary:   Bug 722688 - asm_store64 LIR_std2f cannot have scratch rt == value rv (r=edwsmith+)

http://hg.mozilla.org/tamarin-redux/rev/65e07c19b309

Comment 4

[Edwin Smith]

targetting Brannan, leaving open until it lands in all the right places.  mainline is done.

Comment 5

[Dan Schaffer]

I confirmed the bug is fixed by building FRR and running the dungeon testcase.

Comment 6

[William Maddox]

FRMain CL 1027760
Brannan CL 1027757

Comment 7

[William Maddox]

http://hg.mozilla.org/projects/nanojit-central/rev/8bc1470d3c77