[Mesa-dev] [PATCH] nv50/ir: only stick one preret per function

[Samuel Pitoiset]

On 10/09/2016 06:12 AM, Ilia Mirkin wrote:
> A function with multiple returns would have had multiple preret settings
> at the top of the function. While this is unlikely to have caused issues
> since we don't use funcitons in earnest, it could have in some cases

s/funcitons/functions/ :)

This looks good to me, but fyi this doesn't fix the regressions 
introduced with "nv50/ir: start LocalCSE with getFirst to merge PHI 
instructions". Something else is probably wrong.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>

> overflowed the call stack, in case a function had a lot of early
> returns.
>
> Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
> ---
>  src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
> index 5938226..6664366 100644
> --- a/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
> +++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
> @@ -3475,10 +3475,13 @@ Converter::handleInstruction(const struct tgsi_full_instruction *insn)
>        if (!isEndOfSubroutine(ip + 1)) {
>           // insert a PRERET at the entry if this is an early return
>           // (only needed for sharing code in the epilogue)
> -         BasicBlock *pos = getBB();
> -         setPosition(BasicBlock::get(func->cfg.getRoot()), false);
> -         mkFlow(OP_PRERET, leave, CC_ALWAYS, NULL)->fixed = 1;
> -         setPosition(pos, true);
> +         BasicBlock *root = BasicBlock::get(func->cfg.getRoot());
> +         if (root->getEntry() != NULL && root->getEntry()->op != OP_PRERET) {
> +            BasicBlock *pos = getBB();
> +            setPosition(root, false);
> +            mkFlow(OP_PRERET, leave, CC_ALWAYS, NULL)->fixed = 1;
> +            setPosition(pos, true);
> +         }
>        }
>        mkFlow(OP_RET, NULL, CC_ALWAYS, NULL)->fixed = 1;
>        bb->cfg.attach(&leave->cfg, Graph::Edge::CROSS);
>