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From f2779155495aee6583abaff4700a7acda80864ef Mon Sep 17 00:00:00 2001
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From: Siddhesh Poyarekar <siddhesh@sourceware.org>
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Date: Thu, 28 Mar 2019 10:50:23 +0530
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Subject: [PATCH 72/72] Better behaviour for float to uint32_t conversions
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This is the uint32_t part of the float to unsigned int conversions for
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the interpreter. The cast ends up working correctly for x86 but not
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for aarch64 since fcvtzu sets the result to zero on negative inputs.
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Work slightly harder to make sure that negative number inputs behave
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like x86.
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This fixes the interpreter but not the JIT compiler, which errors out
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during the narrowing pass.
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---
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src/lj_cconv.c | 8 +++++++-
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1 file changed, 7 insertions(+), 1 deletion(-)
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diff --git a/src/lj_cconv.c b/src/lj_cconv.c
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index 13b8230..bf8f8e8 100644
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--- a/src/lj_cconv.c
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+++ b/src/lj_cconv.c
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@@ -196,7 +196,13 @@ void lj_cconv_ct_ct(CTState *cts, CType *d, CType *s,
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else if (dsize == 2) *(int16_t *)dp = (int16_t)i;
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else *(int8_t *)dp = (int8_t)i;
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} else if (dsize == 4) {
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- *(uint32_t *)dp = (uint32_t)n;
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+ /* Undefined behaviour. This is deliberately not a full check because we
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+ * don't want to slow down compliant code. */
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+ lua_assert(n >= -2147483649.0);
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+ if (n > -1.0)
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+ *(uint32_t *)dp = (uint32_t)n;
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+ else
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+ *(uint32_t *)dp = (uint32_t)(int32_t)n;
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} else if (dsize == 8) {
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if (!(dinfo & CTF_UNSIGNED))
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*(int64_t *)dp = (int64_t)n;
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--
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2.20.1
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