x86inc.asm: set PREFIX from libvpx defines

Reapply 4de9641f1

BUG=webm:1679

Change-Id: I70b2224121f8f997fcd04c38a07a8126c2855ec6

diff --git a/third_party/x86inc/README.libvpx_new b/third_party/x86inc/README.libvpx_new
index 6bb81656b872aa9068487812b92276cff39f79aa..f0738ad889d6f71d3da8fca5b05b4ec4279478ea 100644 (file)
--- a/third_party/x86inc/README.libvpx_new
+++ b/third_party/x86inc/README.libvpx_new
@@ -10,3 +10,5 @@ defines that help automatically allow assembly to work cross-platform.
 Local Modifications:
 Get configuration from vpx_config.asm.
 Prefix functions with vpx by default.
+Manage name mangling (prefixing with '_') manually because 'PREFIX' does not
+  exist in libvpx.

diff --git a/third_party/x86inc/x86inc.asm_new b/third_party/x86inc/x86inc.asm_new
index 7b10249f4f955979e4028e8dba0d7c1a6f7e20a6..8a3845c90b6a3daf0b13f3b452867745d2d14546 100644 (file)
--- a/third_party/x86inc/x86inc.asm_new
+++ b/third_party/x86inc/x86inc.asm_new
@@ -82,6 +82,15 @@
     %define FORMAT_MACHO 1
 %endif
 
+; Set PREFIX for libvpx builds.
+%if FORMAT_ELF
+    %undef PREFIX
+%elif WIN64
+    %undef PREFIX
+%else
+    %define PREFIX
+%endif
+
 %ifdef PREFIX
     %define mangle(x) _ %+ x
 %else