From a407780915469a7352b2ca8b0b6d698b0d82bd3f Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 20 Sep 2024 22:05:28 -0400
Subject: [PATCH] CMakeLists.txt: check /proc/cpuinfo for an SV39 MMU

If the host has an SV39 MMU, the usual aligned hinting strategy will
not work despite the system being 64-bit. On RISC-V linux systems, the
type of MMU can be read from /proc/cpuinfo. If we find one, a constant
is defined that will allow us to skip the aligned hinting when the
time comes.
---
 CMakeLists.txt | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bcfe91d8..20b22c09 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -343,6 +343,16 @@ if(MINGW)
   add_definitions(-D_WIN32_WINNT=0x600)
 endif()
 
+# Check /proc/cpuinfo for an SV39 MMU and define a constant if one is
+# found. We will want to skip the aligned hinting in that case.
+if (EXISTS /proc/cpuinfo)
+  file(STRINGS /proc/cpuinfo mi_sv39_mmu REGEX "^mmu[ \t]+:[ \t]+sv39$")
+  if (mi_sv39_mmu)
+    MESSAGE( STATUS "SV39 MMU detected" )
+    list(APPEND mi_defines MI_SV39_MMU=1)
+  endif()
+endif()
+
 # extra needed libraries
 
 # we prefer -l<lib> test over `find_library` as sometimes core libraries