File 1204-clean-up-FP-exception-code-in-sys_float.c.patch of Package erlang
From 4e1102cf8c5bc9ae6a8371665ef6aa9de08e653a Mon Sep 17 00:00:00 2001
From: Mikael Pettersson <mikpelinux@gmail.com>
Date: Sun, 17 Apr 2016 20:24:32 +0200
Subject: [PATCH] clean up FP exception code in sys_float.c
This performs a number of cleanups in the FP exception code:
- inline the body of unmask_fpe_conditional() in its only caller,
then delete the duplicated and identical definitions of it
- start the big processor-specific block with a comment describing
the two functions that must be defined, then delete redundant
comments at all the mask_*() functions
- add a comment before fpe_sig_action() explaining exactly what
processor-specific action is required of it
- flatten #ifdef nesting in fpe_sig_action()
- move common code in the x86 unmask_fpe() and erts_restore_fpu()
function into a subroutine
- minor tweaks: drop a redundant L suffix on a 0, add a comment
after an #else, bump the size of a debug buffer,
There should be no change in behaviour from these changes.
---
erts/emulator/sys/unix/sys_float.c | 79 +++++++++++++++++---------------------
1 file changed, 36 insertions(+), 43 deletions(-)
diff --git a/erts/emulator/sys/unix/sys_float.c b/erts/emulator/sys/unix/sys_float.c
index 8fe7e59..2ac3562 100644
--- a/erts/emulator/sys/unix/sys_float.c
+++ b/erts/emulator/sys/unix/sys_float.c
@@ -53,7 +53,7 @@ static void erts_init_fp_exception(void)
void erts_thread_init_fp_exception(void)
{
unsigned long *fpe = erts_alloc(ERTS_ALC_T_FP_EXCEPTION, sizeof(*fpe));
- *fpe = 0L;
+ *fpe = 0;
erts_tsd_set(fpe_key, fpe);
}
@@ -102,6 +102,17 @@ void erts_fp_check_init_error(volatile unsigned long *fpexnp)
#define __DARWIN__ 1
#endif
+/*
+ * Define two processor and possibly OS-specific primitives:
+ *
+ * static void unmask_fpe(void);
+ * -- unmask invalid, overflow, and divide-by-zero exceptions
+ *
+ * static int mask_fpe(void);
+ * -- mask invalid, overflow, and divide-by-zero exceptions
+ * -- return non-zero if the previous state was unmasked
+ */
+
#if (defined(__i386__) || defined(__x86_64__)) && defined(__GNUC__)
static void unmask_x87(void)
@@ -113,7 +124,6 @@ static void unmask_x87(void)
__asm__ __volatile__("fldcw %0" : : "m"(cw));
}
-/* mask x87 FPE, return true if the previous state was unmasked */
static int mask_x87(void)
{
unsigned short cw;
@@ -136,7 +146,6 @@ static void unmask_sse2(void)
__asm__ __volatile__("ldmxcsr %0" : : "m"(mxcsr));
}
-/* mask SSE2 FPE, return true if the previous state was unmasked */
static int mask_sse2(void)
{
unsigned int mxcsr;
@@ -257,21 +266,19 @@ static int cpu_has_sse2(void)
}
#endif /* !__x86_64__ */
-static void unmask_fpe(void)
+static void unmask_fpe_internal(void)
{
- __asm__ __volatile__("fnclex");
unmask_x87();
if (cpu_has_sse2())
unmask_sse2();
}
-static void unmask_fpe_conditional(int unmasked)
+static void unmask_fpe(void)
{
- if (unmasked)
- unmask_fpe();
+ __asm__ __volatile__("fnclex");
+ unmask_fpe_internal();
}
-/* mask x86 FPE, return true if the previous state was unmasked */
static int mask_fpe(void)
{
int unmasked;
@@ -285,9 +292,7 @@ static int mask_fpe(void)
void erts_restore_fpu(void)
{
__asm__ __volatile__("fninit");
- unmask_x87();
- if (cpu_has_sse2())
- unmask_sse2();
+ unmask_fpe_internal();
}
#elif defined(__sparc__) && defined(__linux__)
@@ -310,13 +315,6 @@ static void unmask_fpe(void)
__asm__ __volatile__(LDX " %0, %%fsr" : : "m"(fsr));
}
-static void unmask_fpe_conditional(int unmasked)
-{
- if (unmasked)
- unmask_fpe();
-}
-
-/* mask SPARC FPE, return true if the previous state was unmasked */
static int mask_fpe(void)
{
unsigned long fsr;
@@ -431,13 +429,6 @@ static void unmask_fpe(void)
set_fpscr(0x80|0x40|0x10); /* VE, OE, ZE; not UE or XE */
}
-static void unmask_fpe_conditional(int unmasked)
-{
- if (unmasked)
- unmask_fpe();
-}
-
-/* mask PowerPC FPE, return true if the previous state was unmasked */
static int mask_fpe(void)
{
int unmasked;
@@ -447,20 +438,13 @@ static int mask_fpe(void)
return unmasked;
}
-#else
+#else /* !(x86 || (sparc && linux) || (powerpc && (linux || darwin))) */
static void unmask_fpe(void)
{
fpsetmask(FP_X_INV | FP_X_OFL | FP_X_DZ);
}
-static void unmask_fpe_conditional(int unmasked)
-{
- if (unmasked)
- unmask_fpe();
-}
-
-/* mask IEEE FPE, return true if previous state was unmasked */
static int mask_fpe(void)
{
const fp_except unmasked_mask = FP_X_INV | FP_X_OFL | FP_X_DZ;
@@ -472,6 +456,16 @@ static int mask_fpe(void)
#endif
+/*
+ * Define a processor and OS-specific SIGFPE handler.
+ *
+ * The effect of receiving a SIGFPE should be:
+ * 1. Update the processor context:
+ * a) on x86: mask FP exceptions, do not skip faulting instruction
+ * b) on SPARC and PowerPC: unmask FP exceptions, skip faulting instruction
+ * 2. call set_current_fp_exception with the PC of the faulting instruction
+ */
+
#if (defined(__linux__) && (defined(__i386__) || defined(__x86_64__) || defined(__sparc__) || defined(__powerpc__))) || (defined(__DARWIN__) && (defined(__i386__) || defined(__x86_64__) || defined(__ppc__))) || (defined(__FreeBSD__) && (defined(__x86_64__) || defined(__i386__))) || ((defined(__NetBSD__) || defined(__OpenBSD__)) && defined(__x86_64__)) || (defined(__sun__) && defined(__x86_64__))
#if defined(__linux__) && defined(__i386__)
@@ -530,8 +524,7 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc)
ucontext_t *uc = puc;
unsigned long pc;
-#if defined(__linux__)
-#if defined(__x86_64__)
+#if defined(__linux__) && defined(__x86_64__)
mcontext_t *mc = &uc->uc_mcontext;
fpregset_t fpstate = mc->fpregs;
pc = mc_pc(mc);
@@ -543,26 +536,26 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc)
set encoding makes that a poor solution here. */
fpstate->mxcsr = 0x1F80;
fpstate->swd &= ~0xFF;
-#elif defined(__i386__)
+#elif defined(__linux__) && defined(__i386__)
mcontext_t *mc = &uc->uc_mcontext;
fpregset_t fpstate = mc->fpregs;
pc = mc_pc(mc);
if ((fpstate->status >> 16) == X86_FXSR_MAGIC)
((struct _fpstate*)fpstate)->mxcsr = 0x1F80;
fpstate->sw &= ~0xFF;
-#elif defined(__sparc__) && defined(__arch64__)
+#elif defined(__linux__) && defined(__sparc__) && defined(__arch64__)
/* on SPARC the 3rd parameter points to a sigcontext not a ucontext */
struct sigcontext *sc = (struct sigcontext*)puc;
pc = sc->sigc_regs.tpc;
sc->sigc_regs.tpc = sc->sigc_regs.tnpc;
sc->sigc_regs.tnpc += 4;
-#elif defined(__sparc__)
+#elif defined(__linux__) && defined(__sparc__)
/* on SPARC the 3rd parameter points to a sigcontext not a ucontext */
struct sigcontext *sc = (struct sigcontext*)puc;
pc = sc->si_regs.pc;
sc->si_regs.pc = sc->si_regs.npc;
sc->si_regs.npc = (unsigned long)sc->si_regs.npc + 4;
-#elif defined(__powerpc__)
+#elif defined(__linux__) && defined(__powerpc__)
#if defined(__powerpc64__)
mcontext_t *mc = &uc->uc_mcontext;
unsigned long *regs = &mc->gp_regs[0];
@@ -573,7 +566,6 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc)
pc = regs[PT_NIP];
regs[PT_NIP] += 4;
regs[PT_FPSCR] = 0x80|0x40|0x10; /* VE, OE, ZE; not UE or XE */
-#endif
#elif defined(__DARWIN__) && (defined(__i386__) || defined(__x86_64__))
#ifdef DARWIN_MODERN_MCONTEXT
mcontext_t mc = uc->uc_mcontext;
@@ -641,7 +633,7 @@ static void fpe_sig_action(int sig, siginfo_t *si, void *puc)
#endif
#if 0
{
- char buf[64];
+ char buf[128];
snprintf(buf, sizeof buf, "%s: FPE at %p\r\n", __FUNCTION__, (void*)pc);
write(2, buf, strlen(buf));
}
@@ -726,7 +718,8 @@ int erts_sys_block_fpe(void)
void erts_sys_unblock_fpe(int unmasked)
{
- unmask_fpe_conditional(unmasked);
+ if (unmasked)
+ unmask_fpe();
}
#endif
--
2.1.4
