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perf: fix LTO build with gcc (hybrid VM) #23606

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perf: fix LTO build with gcc (hybrid VM) #23606

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cfa9928
perf: fix LTO build with gcc (hybrid VM)
henderkes Sep 5, 2026
d5622e6
add i386 registers
henderkes Sep 6, 2026
d89cc39
feedback: add extra host handling in global reg var checks
henderkes Sep 6, 2026
f71b45e
capitalise lto both times
henderkes Sep 6, 2026
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18 changes: 18 additions & 0 deletions Zend/Zend.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -331,6 +331,24 @@ AS_VAR_IF([php_cv_have_global_register_vars], [yes],
])
AC_MSG_CHECKING([whether to enable global register variables support])
AC_MSG_RESULT([$ZEND_GCC_GLOBAL_REGS])

dnl GCC doesn't propagate -ffixed-* from LTO objects. Reserve the VM registers
dnl before LTO code gen to avoid "global register variable follows a function definition"
AS_VAR_IF([ZEND_GCC_GLOBAL_REGS], [yes], [
zend_lto=no
for zend_flag in $CC $CFLAGS $LDFLAGS; do
AS_CASE([$zend_flag], [-flto|-flto=*], [zend_lto=yes], [-fno-lto], [zend_lto=no])
done
AS_VAR_IF([zend_lto], [yes], [
AS_CASE([$host_cpu],
[x86_64*|amd64*], [AS_VAR_APPEND([LDFLAGS], [" -ffixed-r14 -ffixed-r15"])],
[x86*|amd*|i?86*|pentium], [AS_VAR_APPEND([LDFLAGS], [" -ffixed-esi -ffixed-edi"])],
[aarch64*|arm64*], [AS_VAR_APPEND([LDFLAGS], [" -ffixed-x27 -ffixed-x28"])],
[ppc64*|powerpc64*], [AS_VAR_APPEND([LDFLAGS], [" -ffixed-r14 -ffixed-r15"])],
[riscv64*], [AS_VAR_APPEND([LDFLAGS], [" -ffixed-x18 -ffixed-x19"])],
[AC_MSG_ERROR([Cannot reserve VM registers for LTO, disable LTO or use --disable-gcc-global-regs])])
])
])
])

dnl
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2 changes: 2 additions & 0 deletions build/ltmain.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -7705,6 +7705,7 @@ func_mode_link ()
# -tp=* Portland pgcc target processor selection
# --sysroot=* for sysroot support
# -O*, -g*, -flto*, -fwhopr*, -fuse-linker-plugin GCC link-time optimization
# -ffixed-*, -fno-lto GCC LTO register reservations and cancellation
# -specs=* GCC specs files
# -stdlib=* select c++ std lib with clang
# -fdiagnostics-color* simply affects output
Expand All @@ -7725,6 +7726,7 @@ func_mode_link ()
-64|-mips[0-9]|-r[0-9][0-9]*|-xarch=*|-xtarget=*|+DA*|+DD*|-q*|-m*| \
-t[45]*|-txscale*|-p|-pg|--coverage|-fprofile-*|-F*|@*|-tp=*|--sysroot=*| \
-O*|-g*|-flto*|-fwhopr*|-fuse-linker-plugin|-fstack-protector*|-no-canonical-prefixes| \
-ffixed-*|-fno-lto| \
-stdlib=*|-rtlib=*|--unwindlib=*| \
-specs=*|-fsanitize=*|-fno-sanitize*|-shared-libsan|-static-libsan| \
-ffile-prefix-map=*|-fdebug-prefix-map=*|-fmacro-prefix-map=*|-fprofile-prefix-map=*| \
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