Hi!

The following patch saves ~ 2.4GiB of disk space in x86_64-linux
bootstrapped object directory:
find obj80 -name \*.gch -a -type f | xargs du -shc | grep total
3.7G    total
find obj82 -name \*.gch -a -type f | xargs du -shc | grep total
1.3G    total
and ~ 800MiB for i686-linux:
find obj81 -name \*.gch -a -type f | xargs du -shc | grep total
1.2G    total
find obj83 -name \*.gch -a -type f | xargs du -shc | grep total
409M    total
by disabling PCH in stage1/stage2/stageprofile builds, so only
building it in stage3/stagefeedback etc.
I think in stage1/stage2 it is a pure waste of bootstrap time and disk
space, for profiledbootstrap I'd say PCH isn't used commonly enough
in the wild that it is worth training GCC on that (but if you disagree,
I can surely take out that single line in there).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2026-02-04  Jakub Jelinek  <[email protected]>

        * Makefile.tpl (STAGE1_CONFIGURE_FLAGS, STAGE2_CONFIGURE_FLAGS,
        STAGEprofile_CONFIGURE_FLAGS): Append --disable-libstdcxx-pch if
        target-libstdc++-v3-bootstrap.
        * Makefile.in: Regenerate.

--- Makefile.tpl.jj     2026-01-01 18:33:49.674983619 +0100
+++ Makefile.tpl        2026-02-03 23:54:37.609444020 +0100
@@ -556,6 +556,12 @@ STAGE1_CONFIGURE_FLAGS = $(STAGE1_CHECKI
          --disable-coverage --enable-languages="$(STAGE1_LANGUAGES)" \
          --disable-build-format-warnings
 
+@if target-libstdc++-v3-bootstrap
+STAGE1_CONFIGURE_FLAGS += --disable-libstdcxx-pch
+STAGE2_CONFIGURE_FLAGS += --disable-libstdcxx-pch
+STAGEprofile_CONFIGURE_FLAGS += --disable-libstdcxx-pch
+@endif target-libstdc++-v3-bootstrap
+
 @if target-libphobos-bootstrap
 STAGE1_CONFIGURE_FLAGS += --with-libphobos-druntime-only
 STAGE2_CONFIGURE_FLAGS += --with-libphobos-druntime-only
--- Makefile.in.jj      2026-01-01 18:33:49.673983636 +0100
+++ Makefile.in 2026-02-03 23:55:15.755489944 +0100
@@ -633,6 +633,12 @@ STAGE1_CONFIGURE_FLAGS = $(STAGE1_CHECKI
          --disable-coverage --enable-languages="$(STAGE1_LANGUAGES)" \
          --disable-build-format-warnings
 
+@if target-libstdc++-v3-bootstrap
+STAGE1_CONFIGURE_FLAGS += --disable-libstdcxx-pch
+STAGE2_CONFIGURE_FLAGS += --disable-libstdcxx-pch
+STAGEprofile_CONFIGURE_FLAGS += --disable-libstdcxx-pch
+@endif target-libstdc++-v3-bootstrap
+
 @if target-libphobos-bootstrap
 STAGE1_CONFIGURE_FLAGS += --with-libphobos-druntime-only
 STAGE2_CONFIGURE_FLAGS += --with-libphobos-druntime-only

        Jakub

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