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[#1/2] strub: sparc: omit frame in strub_leave [PR112917]

Message ID orjzpg35fe.fsf@lxoliva.fsfla.org
State New
Headers show
Series [#1/2] strub: sparc: omit frame in strub_leave [PR112917] | expand

Commit Message

Alexandre Oliva Dec. 14, 2023, 8:17 p.m. UTC 
If we allow __strub_leave to allocate a frame on sparc, it will
overlap with a lot of the stack range we're supposed to scrub, because
of the large fixed-size outgoing args and register save area.
Unfortunately, setting up the PIC register seems to prevent the frame
pointer from being omitted.

Since the strub runtime doesn't issue calls or use global variables,
at least on sparc, disabling PIC to compile strub.c seems to do the
right thing.

Regstrapped on x86_64-linux-gnu, also testing on sparc-solaris2.11.3.
(but it will likely take forever on the cfarm machine; if someone with
faster sparc machines could give this a spin and confirm, that would be
appreciated.) Ok to install?

IIRC this patch gets 32-bit sparc to pass all strub tests, but sparc64
still fails many of them; there's another one for sparc64 that fixes
them, and that will improve sparc -m32 as well.


for  libgcc/ChangeLog

	PR middle-end/112917
	* config.host (sparc, sparc64): Enable...
	* config/sparc/t-sparc: ... this new fragment.
---
 libgcc/config.host          |    2 ++
 libgcc/config/sparc/t-sparc |    4 ++++
 2 files changed, 6 insertions(+)
 create mode 100644 libgcc/config/sparc/t-sparc
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Patch

diff --git a/libgcc/config.host b/libgcc/config.host
index 694e3e9f54cad..54d06978a5d2c 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -199,9 +199,11 @@  riscv*-*-*)
 	;;
 sparc64*-*-*)
 	cpu_type=sparc
+	tmake_file="${tmake_file} sparc/t-sparc"
 	;;
 sparc*-*-*)
 	cpu_type=sparc
+	tmake_file="${tmake_file} sparc/t-sparc"
 	;;
 s390*-*-*)
 	cpu_type=s390
diff --git a/libgcc/config/sparc/t-sparc b/libgcc/config/sparc/t-sparc
new file mode 100644
index 0000000000000..fb1bf1fc29cc4
--- /dev/null
+++ b/libgcc/config/sparc/t-sparc
@@ -0,0 +1,4 @@ 
+# This is needed for __strub_leave to omit the frame pointer, without
+# which it will allocate a register save area on the stack and leave
+# it unscrubbed and most likely unused, because it's a leaf function.
+CFLAGS-strub.c += -fno-PIC -fomit-frame-pointer