[gcc r15-3585] lto: Stream has_unroll flag during LTO [PR116140]

[Alex Coplan via Gcc-cvs]

https://gcc.gnu.org/g:9759f6299d9633cabac540e5c893341c708093ac

commit r15-3585-g9759f6299d9633cabac540e5c893341c708093ac
Author: Alex Coplan <alex.cop...@arm.com>
Date:   Sat Aug 3 17:02:36 2024 +0000

    lto: Stream has_unroll flag during LTO [PR116140]
    
    When #pragma GCC unroll is processed in
    tree-cfg.cc:replace_loop_annotate_in_block, we set both the loop->unroll
    field (which is currently streamed out and back in during LTO) but also
    the cfun->has_unroll flag.
    
    cfun->has_unroll, however, is not currently streamed during LTO.  This
    patch fixes that.
    
    Prior to this patch, loops marked with #pragma GCC unroll that would be
    unrolled by RTL loop2_unroll in a non-LTO compilation didn't get
    unrolled under LTO.
    
    gcc/ChangeLog:
    
            PR libstdc++/116140
            * lto-streamer-in.cc (input_struct_function_base): Stream in
            fn->has_unroll.
            * lto-streamer-out.cc (output_struct_function_base): Stream out
            fn->has_unroll.
    
    gcc/testsuite/ChangeLog:
    
            PR libstdc++/116140
            * g++.dg/ext/pragma-unroll-lambda-lto.C: New test.

Diff:
---
 gcc/lto-streamer-in.cc                             |  1 +
 gcc/lto-streamer-out.cc                            |  1 +
 .../g++.dg/ext/pragma-unroll-lambda-lto.C          | 32 ++++++++++++++++++++++
 3 files changed, 34 insertions(+)

diff --git a/gcc/lto-streamer-in.cc b/gcc/lto-streamer-in.cc
index 64f758073280..9d0ec5d589c4 100644
--- a/gcc/lto-streamer-in.cc
+++ b/gcc/lto-streamer-in.cc
@@ -1326,6 +1326,7 @@ input_struct_function_base (struct function *fn, class 
data_in *data_in,
   fn->has_force_vectorize_loops = bp_unpack_value (&bp, 1);
   fn->has_simduid_loops = bp_unpack_value (&bp, 1);
   fn->has_musttail = bp_unpack_value (&bp, 1);
+  fn->has_unroll = bp_unpack_value (&bp, 1);
   fn->assume_function = bp_unpack_value (&bp, 1);
   fn->va_list_fpr_size = bp_unpack_value (&bp, 8);
   fn->va_list_gpr_size = bp_unpack_value (&bp, 8);
diff --git a/gcc/lto-streamer-out.cc b/gcc/lto-streamer-out.cc
index a4b171358d41..807b935537be 100644
--- a/gcc/lto-streamer-out.cc
+++ b/gcc/lto-streamer-out.cc
@@ -2283,6 +2283,7 @@ output_struct_function_base (struct output_block *ob, 
struct function *fn)
   bp_pack_value (&bp, fn->has_force_vectorize_loops, 1);
   bp_pack_value (&bp, fn->has_simduid_loops, 1);
   bp_pack_value (&bp, fn->has_musttail, 1);
+  bp_pack_value (&bp, fn->has_unroll, 1);
   bp_pack_value (&bp, fn->assume_function, 1);
   bp_pack_value (&bp, fn->va_list_fpr_size, 8);
   bp_pack_value (&bp, fn->va_list_gpr_size, 8);
diff --git a/gcc/testsuite/g++.dg/ext/pragma-unroll-lambda-lto.C 
b/gcc/testsuite/g++.dg/ext/pragma-unroll-lambda-lto.C
new file mode 100644
index 000000000000..144c4c326924
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/pragma-unroll-lambda-lto.C
@@ -0,0 +1,32 @@
+// { dg-do link { target c++11 } }
+// { dg-options "-O2 -flto -fdump-rtl-loop2_unroll" }
+
+#include <cstdlib>
+
+template<typename Iter, typename Pred>
+inline Iter
+my_find(Iter first, Iter last, Pred pred)
+{
+#pragma GCC unroll 4
+    while (first != last && !pred(*first))
+        ++first;
+    return first;
+}
+
+__attribute__((noipa))
+short *use_find(short *p)
+{
+    auto pred = [](short x) { return x == 42; };
+    return my_find(p, p + 1024, pred);
+}
+
+int main(void)
+{
+  short a[1024];
+  for (int i = 0; i < 1024; i++)
+    a[i] = rand ();
+
+  return use_find (a) - a;
+}
+
+// { dg-final { scan-ltrans-rtl-dump-times "Unrolled loop 3 times" 1 
"loop2_unroll" } }