Hi Andrew! On 2025-07-25T14:44:06+0000, Andrew Stubbs <a...@baylibre.com> wrote: > The optimization options are deliberately passed through to the LTO compiler, > but when the same mechanism is reused for offloading it ends up forcing the > host compiler settings onto the device compiler.
Yeah, that's a problem: for performance-tuning-related 'Param's, as discussed here, but also stuff like <https://gcc.gnu.org/PR114717> "'-fcf-protection' vs. offloading compilation", for example. > Maybe this should be removed > completely What is "this" that you suggest to remove, is it just 'Param's? (That is, classifying them the same as 'Target's ('-m[...]') -- which cannot even be passed through, as they usually don't apply to the heterogeneous offloading back ends.) On the other hand, we want to continue passing through more general flags, like 'Optimization's: '-O', and most (I suppose, but not all...) '-f[...]' ones? > but this patch just fixes a few of them. > In particular, > param_vect_partial_vector_usage is disabled by x86 and this really hurts > amdgcn. > * optc-save-gen.awk: Don't pass through options marked "NoOffload". Please document 'NoOffload' in 'gcc/doc/options.texi'. Do we want '--help=params' to indicate which 'Param's have been tagged 'NoOffload'? > * params.opt (-param=vect-epilogues-nomask): Add NoOffload. > (-param=vect-partial-vector-usage): Likewise. > (-param=vect-inner-loop-cost-factor): Likewise. Do we want to document these three in 'gcc/doc/invoke.texi' as "not passed through to offload compilation", or similar? Grüße Thomas > diff --git a/gcc/optc-save-gen.awk b/gcc/optc-save-gen.awk > index a3d7e5a478e..31756ec380d 100644 > --- a/gcc/optc-save-gen.awk > +++ b/gcc/optc-save-gen.awk > @@ -1313,6 +1313,12 @@ for (i = 0; i < n_opts; i++) { > # offloading is enabled. > if (flag_set_p("Target", flags[i])) > var_target_opt[n_opt_val] = 1; > + > + # These options should not be passed from host to target, but > + # are not actually target specific. > + if (flag_set_p("NoOffload", flags[i])) > + var_target_opt[n_opt_val] = 2; > + > n_opt_val++; > } > } > @@ -1393,7 +1399,7 @@ for (i = 0; i < n_opt_val; i++) { > # Do not stream out target-specific opts if offloading is > # enabled. > if (var_target_opt[i]) > - print " if (!lto_stream_offload_p)" > + print " if (!lto_stream_offload_p) {" > # If applicable, encode the streamed value. > if (var_opt_optimize_init[i]) { > print " if (" var_opt_optimize_init[i] " > (" > var_opt_val_type[i] ") 10)"; > @@ -1403,6 +1409,8 @@ for (i = 0; i < n_opt_val; i++) { > } else { > print " bp_pack_var_len_" sgn " (bp, ptr->" name");"; > } > + if (var_target_opt[i]) > + print "}" > } > } > print " for (size_t i = 0; i < ARRAY_SIZE (ptr->explicit_mask); i++)"; > @@ -1418,10 +1426,14 @@ print " struct > cl_optimization *ptr ATTRIBUTE_UNUSED)" > print "{"; > for (i = 0; i < n_opt_val; i++) { > name = var_opt_val[i] > - if (var_target_opt[i]) { > + if (var_target_opt[i] == 1) { > print "#ifdef ACCEL_COMPILER" > print "#error accel compiler cannot define Optimization > attribute for target-specific option " name; > print "#else" > + } else if (var_target_opt[i] == 2) { > + print "#ifdef ACCEL_COMPILER" > + print " ptr->" name " = global_options." name ";" > + print "#else" > } > otype = var_opt_val_type[i]; > if (otype ~ "^const char \\**$") { > @@ -1489,6 +1501,9 @@ for (i = 0; i < n_opts; i++) { > if (flag_set_p("Warning", flags[i])) > continue; > > + if (flag_set_p("NoOffload", flags[i])) > + continue; > + > if (name in checked_options) > continue; > checked_options[name]++ > diff --git a/gcc/params.opt b/gcc/params.opt > index c7d5fd4d13b..ac1b2c7eb26 100644 > --- a/gcc/params.opt > +++ b/gcc/params.opt > @@ -1226,7 +1226,7 @@ Common Joined UInteger Var(param_use_canonical_types) > Init(1) IntegerRange(0, 1) > Whether to use canonical types. > > -param=vect-epilogues-nomask= > -Common Joined UInteger Var(param_vect_epilogues_nomask) Init(1) > IntegerRange(0, 1) Param Optimization > +Common Joined UInteger Var(param_vect_epilogues_nomask) Init(1) > IntegerRange(0, 1) Param Optimization NoOffload > Enable loop epilogue vectorization using smaller vector size. > > -param=vect-max-layout-candidates= > @@ -1246,11 +1246,11 @@ Common Joined UInteger > Var(param_vect_max_version_for_alignment_checks) Init(6) > Bound on number of runtime checks inserted by the vectorizer's loop > versioning for alignment check. > > -param=vect-partial-vector-usage= > -Common Joined UInteger Var(param_vect_partial_vector_usage) Init(2) > IntegerRange(0, 2) Param Optimization > +Common Joined UInteger Var(param_vect_partial_vector_usage) Init(2) > IntegerRange(0, 2) Param Optimization NoOffload > Controls how loop vectorizer uses partial vectors. 0 means never, 1 means > only for loops whose need to iterate can be removed, 2 means for all loops. > The default value is 2. > > -param=vect-inner-loop-cost-factor= > -Common Joined UInteger Var(param_vect_inner_loop_cost_factor) Init(50) > IntegerRange(1, 10000) Param Optimization > +Common Joined UInteger Var(param_vect_inner_loop_cost_factor) Init(50) > IntegerRange(1, 10000) Param Optimization NoOffload > The maximum factor which the loop vectorizer applies to the cost of > statements in an inner loop relative to the loop being vectorized. > > -param=vect-induction-float=
