[Mesa-dev] [PATCH 2/3] panfrost/midgard: Fix 1-arg ALU memory corruption

[Alyssa Rosenzweig]

Certain ops that only take one argument have an imaginary "zero"
constant for their second argument. For instance, conversions:

   i2f [dest], [source], #0

Memory corruption meant that #0 was instead random noise. For some ops,
that doesn't matter (manifested as abnormally large code size and poor
scheduling due to extra constants in random places). But for others,
where a 1-op is emulated by a 2-op with an implicit 0 second argument,
that broke things.

Fixes iabs (emulated by iabsdiff).

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
---
 src/gallium/drivers/panfrost/midgard/midgard_compile.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/gallium/drivers/panfrost/midgard/midgard_compile.c b/src/gallium/drivers/panfrost/midgard/midgard_compile.c
index 96f3e525b4a..99a648788ef 100644
--- a/src/gallium/drivers/panfrost/midgard/midgard_compile.c
+++ b/src/gallium/drivers/panfrost/midgard/midgard_compile.c
@@ -930,7 +930,8 @@ emit_alu(compiler_context *ctx, nir_alu_instr *instr)
                 }
 
                 ins.alu.src2 = vector_alu_srco_unsigned(blank_alu_src_xxxx);
-        } else if (instr->op == nir_op_f2b32 || instr->op == nir_op_i2b32) {
+        } else if (nr_inputs == 1 && !quirk_flipped_r24) {
+                /* Lots of instructions need a 0 plonked in */
                 ins.ssa_args.inline_constant = false;
                 ins.ssa_args.src1 = SSA_FIXED_REGISTER(REGISTER_CONSTANT);
                 ins.has_constants = true;
-- 
2.20.1