From 7c6faf62158eed309f01bbef8a7b88e0c36459c7 Mon Sep 17 00:00:00 2001
From: ArielG-NV <159081215+ArielG-NV@users.noreply.github.com>
Date: Fri, 7 Jun 2024 09:48:24 -0400
Subject: Precompute UIntSet from individual capabilities inside generator
 (#4269)

* fixes: #4163

Precompute UIntSet from individual capabilities inside generator (removes intermediate form of capabilities).

note:
1. I still expand capabilities which are missing `target` and `stage` atoms.

* fix compile warning<->error with clang

* address review

preallocate the pregenerated UIntSet's

* disable incorrect warning of 'unreachable code'

The warning is wrong since, when `out` has 0 elements (does not start `for` loop), the `return` is reached.

* fix clang warnings

1. use unsigned long for the buffer serializer
2. braces around scalar init

* address review

added work around to avoid warning with `for(...) return; return;` pattern

`else if constexpr` addition instead of cascading blocks

* push fix for use of `_BitScanForward`

* cleanup

* move around assert for proper checking

* syntax error

* use SLANG_ASSERT instead of assert

* test for why SLANG_ASSERT caused CI to fail with linux-arm builds

* test if `SLANG_ASSERT` really is causing a build issue for linux-arm
---
 source/core/slang-uint-set.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'source/core')

diff --git a/source/core/slang-uint-set.h b/source/core/slang-uint-set.h
index 7e08500fd..077bc7981 100644
--- a/source/core/slang-uint-set.h
+++ b/source/core/slang-uint-set.h
@@ -19,8 +19,10 @@ constexpr Index intLog2(unsigned x)
     return x == 1 ? 0 : 1 + intLog2(x >> 1);
 }
 
+// if `in` is 0, result is undefined behavior
 static inline Index bitscanForward(uint64_t in)
 {
+    SLANG_ASSERT(in != 0);
 #if defined(_MSC_VER)
 
 #ifdef _WIN64
@@ -28,14 +30,12 @@ static inline Index bitscanForward(uint64_t in)
     _BitScanForward64((unsigned long*)&out, in);
     return Index(out);
 #else
-    constexpr uint32_t bitsInType = sizeof(uint32_t) * 8;
     uint32_t out;
     // check for 0s in 0bit->31bit. If all 0's, check for 0s in 32bit->63bit
-    _BitScanForward((unsigned long*)&out, *(((uint32_t*)&in) + 1));
-    if (out != bitsInType)
+    if (_BitScanForward((unsigned long*)&out, *(((uint32_t*)&in) + 1)))
         return Index(out);
     _BitScanForward((unsigned long*)&out, *(((uint32_t*)&in)));
-    return Index(out + bitsInType);
+    return Index(out);
 #endif// #ifdef _WIN64
 
 #else 
-- 
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