| From: Ulrich Weigand <ulrich.weigand@de.ibm.com> |
| Date: Fri, 4 Mar 2022 17:41:12 +0100 |
| Subject: [PATCH] Support 64-bit limbs on no-asm platforms |
| |
| Currently, platforms without assembler support always use 32-bit limbs, |
| but the Rust bindings always assume 64-bit limbs. This breaks on |
| big-endian platforms like our IBM Z (s390x). |
| |
| This patch enables 64-bit limbs on 64-bit platforms even if there is |
| no hand-written assembler, by using a 128-bit integer type in the |
| C implementation (this is an extension that is widely supported on |
| 64-bit platforms with GCC or LLVM). |
| |
| Note that this means that the argument "n" to quot_rem_n is no |
| longer guaranteed to always be a multiple of 2, so the corresponding |
| assertion needs to be removed as well. |
| |
| This fixes the broken Rust bindings on IBM Z, and also improves |
| performance by a factor or 3 or more, because compiler-generated |
| code handling __int128 already uses the 64x64->128 multiply |
| instruction our ISA provides. |
| |
| To improve performance of compiler-generated code a bit more, this |
| also switches to the -O3 optimization level, which helps with |
| unrolling of the Montgomery multiply core loop. |
| |
| Upstream-Status: Pending |
| |
| diff --git a/blst/bindings/rust/build.rs b/blst/bindings/rust/build.rs |
| index d823057..093a072 100644 |
| --- a/blst/bindings/rust/build.rs |
| +++ b/blst/bindings/rust/build.rs |
| @@ -234,7 +234,11 @@ fn main() { |
| cc.define("SCRATCH_LIMIT", "(45 * 1024)"); |
| } |
| if !cfg!(debug_assertions) { |
| - cc.opt_level(2); |
| + if target_arch.eq("s390x") { |
| + cc.opt_level(3); |
| + } else { |
| + cc.opt_level(2); |
| + } |
| } |
| cc.files(&file_vec).compile("blst"); |
| |
| diff --git a/blst/src/no_asm.h b/blst/src/no_asm.h |
| index be7bf47..802b78f 100644 |
| --- a/blst/src/no_asm.h |
| +++ b/blst/src/no_asm.h |
| @@ -6,6 +6,8 @@ |
| |
| #if LIMB_T_BITS==32 |
| typedef unsigned long long llimb_t; |
| +#else |
| +typedef unsigned __int128 llimb_t; |
| #endif |
| |
| #if !defined(__STDC_VERSION__) || __STDC_VERSION__<199901 || defined(__STDC_NO_VLA__) |
| @@ -1155,7 +1157,7 @@ limb_t div_3_limbs(const limb_t div_top[2], limb_t d_lo, limb_t d_hi) |
| static limb_t quot_rem_n(limb_t *div_rem, const limb_t *divisor, |
| limb_t quotient, size_t n) |
| { |
| - __builtin_assume(n != 0 && n%2 == 0); |
| + __builtin_assume(n != 0); |
| llimb_t limbx; |
| limb_t tmp[n+1], carry, mask, borrow; |
| size_t i; |
| diff --git a/blst/src/vect.h b/blst/src/vect.h |
| index 19640b1..938a5ff 100644 |
| --- a/blst/src/vect.h |
| +++ b/blst/src/vect.h |
| @@ -18,7 +18,7 @@ typedef unsigned long long limb_t; |
| typedef unsigned __int64 limb_t; |
| # define LIMB_T_BITS 64 |
| |
| -#elif defined(__BLST_NO_ASM__) || defined(__wasm64__) |
| +#elif defined(__wasm64__) |
| typedef unsigned int limb_t; |
| # define LIMB_T_BITS 32 |
| # ifndef __BLST_NO_ASM__ |
| @@ -31,8 +31,10 @@ typedef unsigned long limb_t; |
| # define LIMB_T_BITS 64 |
| # else |
| # define LIMB_T_BITS 32 |
| -# define __BLST_NO_ASM__ |
| # endif |
| +# ifndef __BLST_NO_ASM__ |
| +# define __BLST_NO_ASM__ |
| +# endif |
| #endif |
| |
| /* |
