luajit-Better-behaviour-for-float-to-uint32_t-conversions.patch

From f2779155495aee6583abaff4700a7acda80864ef Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Thu, 28 Mar 2019 10:50:23 +0530
Subject: [PATCH 72/72] Better behaviour for float to uint32_t conversions

This is the uint32_t part of the float to unsigned int conversions for
the interpreter.  The cast ends up working correctly for x86 but not
for aarch64 since fcvtzu sets the result to zero on negative inputs.
Work slightly harder to make sure that negative number inputs behave
like x86.

This fixes the interpreter but not the JIT compiler, which errors out
during the narrowing pass.
---
 src/lj_cconv.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/lj_cconv.c b/src/lj_cconv.c
index 13b8230..bf8f8e8 100644
--- a/src/lj_cconv.c
+++ b/src/lj_cconv.c
@@ -196,7 +196,13 @@ void lj_cconv_ct_ct(CTState *cts, CType *d, CType *s,
       else if (dsize == 2) *(int16_t *)dp = (int16_t)i;
       else *(int8_t *)dp = (int8_t)i;
     } else if (dsize == 4) {
-      *(uint32_t *)dp = (uint32_t)n;
+      /* Undefined behaviour. This is deliberately not a full check because we
+       * don't want to slow down compliant code. */
+      lua_assert(n >= -2147483649.0);
+      if (n > -1.0)
+        *(uint32_t *)dp = (uint32_t)n;
+      else
+        *(uint32_t *)dp = (uint32_t)(int32_t)n;
     } else if (dsize == 8) {
       if (!(dinfo & CTF_UNSIGNED))
 	*(int64_t *)dp = (int64_t)n;
-- 
2.20.1