RISC-V port and assorted changes

This commits adds code generation for the RISC-V architecture, both in 32- and 64-bit modes.

The generated code was lightly tested using the simulator and cross-binutils from https://riscv.org/software-tools/

This port required the following additional changes:

- Integers: More properties about shrx

- SelectOp: now provides smart constructors for mulhs and mulhu

- SelectDiv, 32-bit integer division and modulus: implement constant propagation, use the new smart constructors mulhs and mulhu.

- Runtime library: if no asm implementation is provided, run the reference C implementation through CompCert.  Since CompCert rejects the definitions of names of special functions such as __i64_shl, the reference implementation now uses "i64_" names, e.g. "i64_shl", and a renaming "i64_ -> __i64_" is performed over the generated assembly file, before assembling and building the runtime library.

- test/: add SIMU make variable to run tests through a simulator

- test/regression/alignas.c: make sure _Alignas and _Alignof are not #define'd by C headers

commit da14495c01cf4f66a928c2feff5c53f09bde837f
Author: Xavier Leroy <xavier.leroy@inria.fr>
Date:   Thu Apr 13 17:36:10 2017 +0200

    RISC-V port, continued

    Now working on Asmgen.

commit 36f36eb3a5abfbb8805960443d087b6a83e86005
Author: Xavier Leroy <xavier.leroy@inria.fr>
Date:   Wed Apr 12 17:26:39 2017 +0200

    RISC-V port, first steps

    This port is based on Prashanth Mundkur's experimental RV32 port and brings it up to date with CompCert, and adds 64-bit support (RV64).  Work in progress.

17 files changed, 40 insertions, 40 deletions

diff --git a/runtime/c/i64.h b/runtime/c/i64.h
index a75214fe..3f59164b 100644
--- a/runtime/c/i64.h
+++ b/runtime/c/i64.h
@@ -34,12 +34,12 @@
 
 /* Helper functions for 64-bit integer arithmetic. Reference C implementation */
 
-extern unsigned long long __i64_shl(unsigned long long x, int amount);
-extern unsigned long long __i64_shr(unsigned long long x, int amount);
-extern signed long long __i64_sar(signed long long x, int amount);
+extern unsigned long long i64_shl(unsigned long long x, int amount);
+extern unsigned long long i64_shr(unsigned long long x, int amount);
+extern signed long long i64_sar(signed long long x, int amount);
 
-extern unsigned long long __i64_udivmod(unsigned long long n,
+extern unsigned long long i64_udivmod(unsigned long long n,
                                         unsigned long long d,
                                         unsigned long long * rp);
-extern unsigned long long __i64_umulh(unsigned long long u,
+extern unsigned long long i64_umulh(unsigned long long u,
                                       unsigned long long v);
diff --git a/runtime/c/i64_dtos.c b/runtime/c/i64_dtos.c
index d428e744..5d12bf4b 100644
--- a/runtime/c/i64_dtos.c
+++ b/runtime/c/i64_dtos.c
@@ -38,7 +38,7 @@
 
 /* Conversion float64 -> signed int64 */
 
-long long __i64_dtos(double d)
+long long i64_dtos(double d)
 {
   /* Extract bits of d's representation */
   union { double d; unsigned long long i; } buf;
@@ -63,9 +63,9 @@ long long __i64_dtos(double d)
     (buf.i & ~0xFFF0000000000000LL) | 0x0010000000000000LL;
   /* Shift it appropriately */
   if (e >= 0)
-    m = __i64_shl(m, e);
+    m = i64_shl(m, e);
   else
-    m = __i64_shr(m, -e);
+    m = i64_shr(m, -e);
   /* Apply sign to result */
   if ((int) h < 0)
     return -m;
diff --git a/runtime/c/i64_dtou.c b/runtime/c/i64_dtou.c
index c5f9df4d..5f4901b2 100644
--- a/runtime/c/i64_dtou.c
+++ b/runtime/c/i64_dtou.c
@@ -38,7 +38,7 @@
 
 /* Conversion float64 -> unsigned int64 */
 
-unsigned long long __i64_dtou(double d)
+unsigned long long i64_dtou(double d)
 {
   /* Extract bits of d's representation */
   union { double d; unsigned long long i; } buf;
@@ -62,8 +62,8 @@ unsigned long long __i64_dtou(double d)
     (buf.i & ~0xFFF0000000000000LL) | 0x0010000000000000LL;
   /* Shift it appropriately */
   if (e >= 0)
-    return __i64_shl(m, e);
+    return i64_shl(m, e);
   else
-    return __i64_shr(m, -e);
+    return i64_shr(m, -e);
 
 }
diff --git a/runtime/c/i64_sar.c b/runtime/c/i64_sar.c
index a5f3364a..611aa047 100644
--- a/runtime/c/i64_sar.c
+++ b/runtime/c/i64_sar.c
@@ -38,7 +38,7 @@
 
 /* Shift right signed */
 
-signed long long __i64_sar(signed long long x, int amount)
+signed long long i64_sar(signed long long x, int amount)
 {
   unsigned xl = x;
   int xh = x >> 32;
diff --git a/runtime/c/i64_sdiv.c b/runtime/c/i64_sdiv.c
index 3f21d9b7..20faf121 100644
--- a/runtime/c/i64_sdiv.c
+++ b/runtime/c/i64_sdiv.c
@@ -38,14 +38,14 @@
 
 /* Signed division */
 
-signed long long __i64_sdiv(signed long long n, signed long long d)
+signed long long i64_sdiv(signed long long n, signed long long d)
 {
   unsigned long long un, ud, uq, ur;
   int nh = n >> 32, dh = d >> 32;
   /* Take absolute values of n and d */
   un = nh < 0 ? -n : n;
   ud = dh < 0 ? -d : d;
-  uq = __i64_udivmod(un, ud, &ur);
+  uq = i64_udivmod(un, ud, &ur);
   /* Apply sign to quotient */
   return (nh ^ dh) < 0 ? -uq : uq;
 }
diff --git a/runtime/c/i64_shl.c b/runtime/c/i64_shl.c
index 9b9aae57..186d2d32 100644
--- a/runtime/c/i64_shl.c
+++ b/runtime/c/i64_shl.c
@@ -38,7 +38,7 @@
 
 /* Shift left */
 
-unsigned long long __i64_shl(unsigned long long x, int amount)
+unsigned long long i64_shl(unsigned long long x, int amount)
 {
   unsigned xl = x, xh = x >> 32;
   amount = amount & 63;
diff --git a/runtime/c/i64_shr.c b/runtime/c/i64_shr.c
index c1db2a5f..bb2facce 100644
--- a/runtime/c/i64_shr.c
+++ b/runtime/c/i64_shr.c
@@ -38,7 +38,7 @@
 
 /* Shift right unsigned */
 
-unsigned long long __i64_shr(unsigned long long x, int amount)
+unsigned long long i64_shr(unsigned long long x, int amount)
 {
   unsigned xl = x, xh = x >> 32;
   amount = amount & 63;
diff --git a/runtime/c/i64_smod.c b/runtime/c/i64_smod.c
index ab15b6e6..b0f2c3cd 100644
--- a/runtime/c/i64_smod.c
+++ b/runtime/c/i64_smod.c
@@ -38,14 +38,14 @@
 
 /* Signed remainder */
 
-signed long long __i64_smod(signed long long n, signed long long d)
+signed long long i64_smod(signed long long n, signed long long d)
 {
   unsigned long long un, ud, ur;
   int nh = n >> 32, dh = d >> 32;
   /* Take absolute values of n and d */
   un = nh < 0 ? -n : n;
   ud = dh < 0 ? -d : d;
-  (void) __i64_udivmod(un, ud, &ur);
+  (void) i64_udivmod(un, ud, &ur);
   /* Apply sign to remainder */
   return nh < 0 ? -ur : ur;
 }
diff --git a/runtime/c/i64_smulh.c b/runtime/c/i64_smulh.c
index b7a42474..3b33d375 100644
--- a/runtime/c/i64_smulh.c
+++ b/runtime/c/i64_smulh.c
@@ -47,9 +47,9 @@ typedef unsigned long long u64;
  * - subtract Y if X < 0 
  */
 
-s64 __i64_smulh(s64 x, s64 y)
+s64 i64_smulh(s64 x, s64 y)
 {
-  s64 t = (s64) __i64_umulh(x, y);
+  s64 t = (s64) i64_umulh(x, y);
   if (y < 0) t = t - x;
   if (x < 0) t = t - y;
   return t;
diff --git a/runtime/c/i64_stod.c b/runtime/c/i64_stod.c
index 158b6892..b5b6a7bc 100644
--- a/runtime/c/i64_stod.c
+++ b/runtime/c/i64_stod.c
@@ -38,7 +38,7 @@
 
 /* Conversion from signed int64 to float64 */
 
-double __i64_stod(signed long long x)
+double i64_stod(signed long long x)
 {
   unsigned xl = x;
   signed xh = x >> 32;
diff --git a/runtime/c/i64_stof.c b/runtime/c/i64_stof.c
index 8410ba13..12406421 100644
--- a/runtime/c/i64_stof.c
+++ b/runtime/c/i64_stof.c
@@ -38,7 +38,7 @@
 
 /* Conversion from signed int64 to float32 */
 
-float __i64_stof(signed long long x)
+float i64_stof(signed long long x)
 {
   if (x < -(1LL << 53) || x >= (1LL << 53)) {
     /* x is large enough that double rounding can occur.
diff --git a/runtime/c/i64_udiv.c b/runtime/c/i64_udiv.c
index 91fbf6e4..19d9264d 100644
--- a/runtime/c/i64_udiv.c
+++ b/runtime/c/i64_udiv.c
@@ -38,8 +38,8 @@
 
 /* Unsigned division */
 
-unsigned long long __i64_udiv(unsigned long long n, unsigned long long d)
+unsigned long long i64_udiv(unsigned long long n, unsigned long long d)
 {
   unsigned long long r;
-  return __i64_udivmod(n, d, &r);
+  return i64_udivmod(n, d, &r);
 }
diff --git a/runtime/c/i64_udivmod.c b/runtime/c/i64_udivmod.c
index d8f5073a..03efbc9d 100644
--- a/runtime/c/i64_udivmod.c
+++ b/runtime/c/i64_udivmod.c
@@ -37,13 +37,13 @@
 #include <stddef.h>
 #include "i64.h"
 
-static unsigned __i64_udiv6432(unsigned u1, unsigned u0,
+static unsigned i64_udiv6432(unsigned u1, unsigned u0,
                                unsigned v, unsigned *r);
-static int __i64_nlz(unsigned x);
+static int i64_nlz(unsigned x);
 
 /* Unsigned division and remainder */
 
-unsigned long long __i64_udivmod(unsigned long long n,
+unsigned long long i64_udivmod(unsigned long long n,
                                  unsigned long long d,
                                  unsigned long long * rp)
 {
@@ -62,7 +62,7 @@ unsigned long long __i64_udivmod(unsigned long long n,
       unsigned dl = d; 
       unsigned qh = nh / dl;
       unsigned rl;
-      unsigned ql = __i64_udiv6432(nh % dl, nl, dl, &rl);
+      unsigned ql = i64_udiv6432(nh % dl, nl, dl, &rl);
       *rp = (unsigned long long) rl; /* high word of remainder is 0 */
       return ((unsigned long long) qh) << 32 | ql;
     }
@@ -70,11 +70,11 @@ unsigned long long __i64_udivmod(unsigned long long n,
     /* General case 64 / 64 */
     unsigned dl = d;
     /* Scale N and D down, giving N' and D' such that 2^31 <= D' < 2^32 */
-    int s = 32 - __i64_nlz(dh);  /* shift amount, between 1 and 32 */
-    unsigned long long np = __i64_shr(n, s);
-    unsigned dp = (unsigned) __i64_shr(d, s);
+    int s = 32 - i64_nlz(dh);  /* shift amount, between 1 and 32 */
+    unsigned long long np = i64_shr(n, s);
+    unsigned dp = (unsigned) i64_shr(d, s);
     /* Divide N' by D' to get an approximate quotient Q */
-    unsigned q = __i64_udiv6432(np >> 32, np, dp, NULL);
+    unsigned q = i64_udiv6432(np >> 32, np, dp, NULL);
   again: ;
     /* Tentative quotient Q is either correct or one too high */
     /* Compute Q * D, checking for overflow */
@@ -99,7 +99,7 @@ unsigned long long __i64_udivmod(unsigned long long n,
 /* Unsigned division and remainder for 64 bits divided by 32 bits. */
 /* This is algorithm "divlu" from _Hacker's Delight_, fig 9.3 */
 
-static unsigned __i64_udiv6432(unsigned u1, unsigned u0,
+static unsigned i64_udiv6432(unsigned u1, unsigned u0,
                                unsigned v, unsigned *r)
 {
   const unsigned b = 65536; // Number base (16 bits).
@@ -114,7 +114,7 @@ static unsigned __i64_udiv6432(unsigned u1, unsigned u0,
     if (r != NULL) *r = 0xFFFFFFFFU; // set rem to an impossible value,
     return 0xFFFFFFFFU;              // and return largest possible quotient.
   }
-  s = __i64_nlz(v);          // 0 <= s <= 31.
+  s = i64_nlz(v);          // 0 <= s <= 31.
   v = v << s;                // Normalize divisor.
   vn1 = v >> 16;             // Break divisor up into
   vn0 = v & 0xFFFF;          // two 16-bit digits.
@@ -145,7 +145,7 @@ again2:
 
 /* Number of leading zeroes */
 
-static int __i64_nlz(unsigned x)
+static int i64_nlz(unsigned x)
 {
   if (x == 0) return 32;
   int n = 0;
diff --git a/runtime/c/i64_umod.c b/runtime/c/i64_umod.c
index d30e29c4..37640d5f 100644
--- a/runtime/c/i64_umod.c
+++ b/runtime/c/i64_umod.c
@@ -38,9 +38,9 @@
 
 /* Unsigned remainder */
 
-unsigned long long __i64_umod(unsigned long long n, unsigned long long d)
+unsigned long long i64_umod(unsigned long long n, unsigned long long d)
 {
   unsigned long long r;
-  (void) __i64_udivmod(n, d, &r);
+  (void) i64_udivmod(n, d, &r);
   return r;
 }
diff --git a/runtime/c/i64_umulh.c b/runtime/c/i64_umulh.c
index d2394d09..a2e33f5d 100644
--- a/runtime/c/i64_umulh.c
+++ b/runtime/c/i64_umulh.c
@@ -43,7 +43,7 @@ typedef unsigned int u32;
 
 /* Hacker's Delight, algorithm 8.1, specialized to two 32-bit words */
 
-u64 __i64_umulh(u64 u, u64 v)
+u64 i64_umulh(u64 u, u64 v)
 {
   u32 u0 = u, u1 = u >> 32;
   u32 v0 = v, v1 = v >> 32;
diff --git a/runtime/c/i64_utod.c b/runtime/c/i64_utod.c
index e70820a9..7210c73c 100644
--- a/runtime/c/i64_utod.c
+++ b/runtime/c/i64_utod.c
@@ -38,7 +38,7 @@
 
 /* Conversion from unsigned int64 to float64 */
 
-double __i64_utod(unsigned long long x)
+double i64_utod(unsigned long long x)
 {
   unsigned xl = x, xh = x >> 32;
   return (double) xl + 0x1.0p32 * (double) xh;
diff --git a/runtime/c/i64_utof.c b/runtime/c/i64_utof.c
index 87b85bfc..77a23765 100644
--- a/runtime/c/i64_utof.c
+++ b/runtime/c/i64_utof.c
@@ -38,7 +38,7 @@
 
 /* Conversion from unsigned int64 to float32 */
 
-float __i64_utof(unsigned long long x)
+float i64_utof(unsigned long long x)
 {
   if (x >= 1ULL << 53) {
     /* x is large enough that double rounding can occur.