1229802 - Simplify MacroAssemblerARMCompat::decBranchPtr.

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Tooru Fujisawa [:arai]]

derived from bug 1229057 comment #30.

https://dxr.mozilla.org/mozilla-central/rev/470f4f8c2b2d6f82e56e161a4b05262c85f55b59/js/src/jit/arm/MacroAssembler-arm.h#985
>     void decBranchPtr(Condition cond, Register lhs, Imm32 imm, Label* label) {
>         subPtr(imm, lhs);
>         branch32(cond, lhs, Imm32(0), label);
>     }

branch32 calls ma_cmp with SetCC, but ma_sub called in subPtr can also called with SetCC.  We could replace them with ma_sub(..., SetCC) + j() or something


note that bug 1229057 will move the definition of decBranchPtr to MacroAssembler-arm-inl.h

Comment 1

[Tooru Fujisawa [:arai]]

Attachment: Simplify MacroAssemblerARMCompat::decBranchPtr.

Changed to almost same code as branchSub32.

Green on try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=302d5fb58843

Comment 2

[Nicolas B. Pierron [:nbp]]

Comment on attachment 8700396 [details] [diff] [review]
Simplify MacroAssemblerARMCompat::decBranchPtr.

Review of attachment 8700396 [details] [diff] [review]:
-----------------------------------------------------------------

Good catch!

::: js/src/jit/arm/MacroAssembler-arm.h
@@ +972,5 @@
>          branch32(cond, lhs, imm, label);
>      }
> +    void decBranchPtr(Condition cond, Register lhs, Imm32 imm, Label* label) {
> +        ma_sub(imm, lhs, SetCC);
> +        j(cond, label);

nit: "j" is a x86-ism, prefer "as_b" instead.

Comment 3

[Tooru Fujisawa [:arai]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/6296b4d5aff39444292bdfd5c59a5a572ab771ad
Bug 1229802 - Simplify MacroAssemblerARMCompat::decBranchPtr. r=nbp

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/6296b4d5aff3