From b1388039a50cccd6dce7fbf35a295e414d4a2f49 Mon Sep 17 00:00:00 2001
From: Stan Hu <stanhu@gmail.com>
Date: Fri, 10 Sep 2021 12:01:17 -0700
Subject: [PATCH] Drop -msse4 compiler flag

Older CPUs that do not have SSE4.1 would crash with the Ruby native gem
due to an illegal instruction exception.

The Abseil random library isn't being used at the moment
(https://github.com/grpc/grpc/pull/26476), and there's no reason gRPC
needs to force SSE4.1 instructions on all platforms at the moment. There
are other hardware-specific issues that need to be ironed out for this
to work: https://github.com/grpc/grpc/pull/26479

When the `-msse4` compiler flag was enabled, the Abseil code started
using the `pinsrb` instruction:

```
$ elfx86exts abseil-cpp/absl/time/internal/cctz/src/time_zone_libc.o
MODE64 (ret)
CMOV (cmovne)
SSE2 (movdqa)
SSE41 (pinsrb)
SSE1 (movaps)
CPU Generation: Penryn
```

This was previously needed because gcc 4.8 wouldn't compile without the
`-msse4` and `-maes` flags.

However, per
https://github.com/gcc-mirror/gcc/commit/97db2bf7fb10e7eb2e8224e0471b56976f133843
gcc 5.0+ automatically detects whether these options are enabled.

clang still needs `-maes` since including `wmmintrin.h` expects the AES
option to be enabled.

Closes https://github.com/grpc/grpc/issues/27095
---
 Makefile                    | 2 +-
 templates/Makefile.template | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index fd98ab5a60a6d..303c46e60f24d 100644
--- a/Makefile
+++ b/Makefile
@@ -579,7 +579,7 @@ CPPFLAGS := -Ithird_party/address_sorting/include $(CPPFLAGS)
 GRPC_ABSEIL_DEP = $(LIBDIR)/$(CONFIG)/libgrpc_abseil.a
 GRPC_ABSEIL_MERGE_LIBS = $(LIBDIR)/$(CONFIG)/libgrpc_abseil.a
 ifeq ($(HOST_IS_X86_64),true)
-ABSL_RANDOM_HWAES_FLAGS = -maes -msse4
+ABSL_RANDOM_HWAES_FLAGS = -maes
 else
 ABSL_RANDOM_HWAES_FLAGS =
 endif
diff --git a/templates/Makefile.template b/templates/Makefile.template
index 5afb36ce6a47f..7e47866b37e48 100644
--- a/templates/Makefile.template
+++ b/templates/Makefile.template
@@ -442,7 +442,7 @@
   GRPC_ABSEIL_DEP = $(LIBDIR)/$(CONFIG)/libgrpc_abseil.a
   GRPC_ABSEIL_MERGE_LIBS = $(LIBDIR)/$(CONFIG)/libgrpc_abseil.a
   ifeq ($(HOST_IS_X86_64),true)
-  ABSL_RANDOM_HWAES_FLAGS = -maes -msse4
+  ABSL_RANDOM_HWAES_FLAGS = -maes
   else
   ABSL_RANDOM_HWAES_FLAGS =
   endif