[Guile-commits] 273/437: x86: Ensure the x87 stack is empty when calling a function.

[Andy Wingo]

wingo pushed a commit to branch lightning
in repository guile.

commit 0b0d63d89293475409161e86ae727087a14d99b1
Author: pcpa <address@hidden>
Date:   Tue Dec 3 15:09:48 2013 -0200

    x86: Ensure the x87 stack is empty when calling a function.
    
        * lib/jit_x86-cpu.c: Use the emms instruction before
        calling any function. This is particularly important
        when using c99 complex functions as it can easily
        overflow the x87 stack due to the way lightning uses
        the x87 stack as a flat register file.
---
 ChangeLog         | 8 ++++++++
 lib/jit_x86-cpu.c | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index eef5617..8eaed7a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2013-12-03 Paulo Andrade <address@hidden>
+
+       * lib/jit_x86-cpu.c: Use the emms instruction before
+       calling any function. This is particularly important
+       when using c99 complex functions as it can easily
+       overflow the x87 stack due to the way lightning uses
+       the x87 stack as a flat register file.
+
 2013-12-02 Paulo Andrade <address@hidden>
 
        * lib/jit_x86-x87.c: Correct wrong code generation due
diff --git a/lib/jit_x86-cpu.c b/lib/jit_x86-cpu.c
index 4cf16c1..e79697a 100644
--- a/lib/jit_x86-cpu.c
+++ b/lib/jit_x86-cpu.c
@@ -139,6 +139,7 @@ static void
 _rx(jit_state_t*,jit_int32_t,jit_int32_t,jit_int32_t,jit_int32_t,jit_int32_t);
 #  define nop(n)                       _nop(_jit, n)
 static void _nop(jit_state_t*, jit_int32_t);
+#  define emms()                       is(0x770f)
 #  define lea(md, rb, ri, ms, rd)      _lea(_jit, md, rb, ri, ms, rd)
 static void
 _lea(jit_state_t*,jit_int32_t,jit_int32_t,jit_int32_t,jit_int32_t,jit_int32_t);
@@ -3258,6 +3259,9 @@ _bxsubi_u(jit_state_t *_jit, jit_word_t i0, jit_int32_t 
r0, jit_word_t i1)
 static void
 _callr(jit_state_t *_jit, jit_int32_t r0)
 {
+#if __WORDSIZE == 32
+    emms();
+#endif
     rex(0, 0, _NOREG, _NOREG, r0);
     ic(0xff);
     mrm(0x03, 0x02, r7(r0));
@@ -3276,6 +3280,7 @@ _calli(jit_state_t *_jit, jit_word_t i0)
     jit_unget_reg(reg);
 #else
     jit_word_t         w;
+    emms();
     ic(0xe8);
     w = i0 - (_jit->pc.w + 4);
     ii(w);