From: Andrew Burgess <aburgess@redhat.com>
Date: Wed, 19 Oct 2022 14:12:57 +0000 (+0100)
Subject: sim/ppc: fix for operator precedence warning from clang
X-Git-Tag: gdb-13-branchpoint~735
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e0b3df3b4d77706abf5f077477b2ca227fc4e9d1;p=thirdparty%2Fbinutils-gdb.git

sim/ppc: fix for operator precedence warning from clang

In the ppc simulator, clang was warning about some code like this:

  busy_ptr->nr_writebacks = 1 + (PPC_ONE_BIT_SET_P(out_vmask)) ? 1 : 2;

The warning was:

  operator '?:' has lower precedence than '+'; '+' will be evaluated first

I suspect that this is not the original authors intention.
PPC_ONE_BIT_SET_P is going to be 0 or 1, so if we evaluate the '+'
first, the condition will always be non-zero, so true.  The whole
expression could then be simplified to just '1', which doesn't make
much sense.

I suspect the answer the author was expecting was either 2 or 3.  Why
they didn't just write:

  busy_ptr->nr_writebacks = (PPC_ONE_BIT_SET_P(out_vmask)) ? 2 : 3;

I have no clue, however, to keep the structure of the code unchanged,
I've updated things to:

  busy_ptr->nr_writebacks = 1 + (PPC_ONE_BIT_SET_P (out_vmask) ? 1 : 2);

which silences the warning from clang, and is, I am guessing, what the
original author intended.
---

diff --git a/sim/ppc/altivec.igen b/sim/ppc/altivec.igen
index 63fe95a53d5..f3ad32d8825 100644
--- a/sim/ppc/altivec.igen
+++ b/sim/ppc/altivec.igen
@@ -231,7 +231,7 @@ void::model-function::ppc_insn_vr_vscr:itable_index index, model_data *model_ptr
 	busy_ptr->vscr_busy = 1;
 
 	if (out_vmask)
-	  busy_ptr->nr_writebacks = 1 + (PPC_ONE_BIT_SET_P(out_vmask)) ? 1 : 2;
+	  busy_ptr->nr_writebacks = 1 + (PPC_ONE_BIT_SET_P (out_vmask) ? 1 : 2);
 
 	if (WITH_TRACE && ppc_trace[trace_model])
 	  model_trace_altivec_make_busy(model_ptr, vr_mask, 0);