Mesa (master): llvmpipe: Avoid corrupting the FPU stack with MMX instructions on 32bit OSes.
Jose Fonseca
jrfonseca at kemper.freedesktop.org
Thu Jul 29 18:19:40 UTC 2010
Module: Mesa
Branch: master
Commit: e3d2ebac115f7b7899664fefc2652fb829acfa27
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=e3d2ebac115f7b7899664fefc2652fb829acfa27
Author: José Fonseca <jfonseca at vmware.com>
Date: Thu Jul 22 18:37:46 2010 +0100
llvmpipe: Avoid corrupting the FPU stack with MMX instructions on 32bit OSes.
Unfortunately LLVM doesn't emit EMMS itself, and there is no
easy/effective way to disable MMX.
http://llvm.org/bugs/show_bug.cgi?id=3287
---
src/gallium/auxiliary/gallivm/lp_bld_misc.cpp | 24 ++++++++++++++++++++++++
src/gallium/drivers/llvmpipe/lp_state_fs.c | 5 +++++
2 files changed, 29 insertions(+), 0 deletions(-)
diff --git a/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp b/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
index 5a9488b..072408b 100644
--- a/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
+++ b/src/gallium/auxiliary/gallivm/lp_bld_misc.cpp
@@ -39,6 +39,7 @@
#include <llvm/Target/TargetOptions.h>
#include <llvm/ExecutionEngine/ExecutionEngine.h>
#include <llvm/ExecutionEngine/JITEventListener.h>
+#include <llvm/Support/CommandLine.h>
#include "pipe/p_config.h"
#include "util/u_debug.h"
@@ -141,4 +142,27 @@ lp_set_target_options(void)
#if 0
llvm::UnsafeFPMath = true;
#endif
+
+#if 0
+ /*
+ * LLVM will generate MMX instructions for vectors <= 64 bits, leading to
+ * innefficient code, and in 32bit systems, to the corruption of the FPU
+ * stack given that it expects the user to generate the EMMS instructions.
+ *
+ * See also:
+ * - http://llvm.org/bugs/show_bug.cgi?id=3287
+ * - http://l4.me.uk/post/2009/06/07/llvm-wrinkle-3-configuration-what-configuration/
+ *
+ * XXX: Unfortunately this is not working.
+ */
+ static boolean first = FALSE;
+ if (first) {
+ static const char* options[] = {
+ "prog",
+ "-disable-mmx"
+ };
+ llvm::cl::ParseCommandLineOptions(2, const_cast<char**>(options));
+ first = FALSE;
+ }
+#endif
}
diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index 5953d69..dbcc286 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -676,6 +676,11 @@ generate_fragment(struct llvmpipe_context *lp,
color_ptr);
}
+#ifdef PIPE_ARCH_X86
+ /* Avoid corrupting the FPU stack on 32bit OSes. */
+ lp_build_intrinsic(builder, "llvm.x86.mmx.emms", LLVMVoidType(), NULL, 0);
+#endif
+
LLVMBuildRetVoid(builder);
LLVMDisposeBuilder(builder);
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