[compiler-rt] [builtins] Use __builtin_clzll for 64-bit types (PR #99874)

[Sergei Barannikov via llvm-commits]

https://github.com/s-barannikov created https://github.com/llvm/llvm-project/pull/99874

This addresses the issue with __LP64__ not being defined for targets with 32-bit pointers but 64-bit longs, resulting in worse codegen.

>From 50ea81240a441307278c0fa5a73ffcb0db57de85 Mon Sep 17 00:00:00 2001
From: Sergei Barannikov <barannikov88 at gmail.com>
Date: Mon, 22 Jul 2024 16:36:32 +0300
Subject: [PATCH] [builtins] Use __builtin_clzll for 64-bit types

This addresses the issue with __LP64__ not being defined for targets
with 32-bit pointers but 64-bit longs, resulting in worse codegen.
---
 compiler-rt/lib/builtins/fp_extend.h |  9 +--------
 compiler-rt/lib/builtins/fp_lib.h    | 11 ++---------
 2 files changed, 3 insertions(+), 17 deletions(-)

diff --git a/compiler-rt/lib/builtins/fp_extend.h b/compiler-rt/lib/builtins/fp_extend.h
index 7637417649e62..3cde433fca3ea 100644
--- a/compiler-rt/lib/builtins/fp_extend.h
+++ b/compiler-rt/lib/builtins/fp_extend.h
@@ -38,14 +38,7 @@ static const int srcSigFracBits = 52;
 static const int srcExpBits = 11;
 
 static inline int src_rep_t_clz_impl(src_rep_t a) {
-#if defined __LP64__
-  return __builtin_clzl(a);
-#else
-  if (a & REP_C(0xffffffff00000000))
-    return clzsi(a >> 32);
-  else
-    return 32 + clzsi(a & REP_C(0xffffffff));
-#endif
+  return __builtin_clzll(a);
 }
 #define src_rep_t_clz src_rep_t_clz_impl
 
diff --git a/compiler-rt/lib/builtins/fp_lib.h b/compiler-rt/lib/builtins/fp_lib.h
index 8404d98c93508..17bf9913fe24f 100644
--- a/compiler-rt/lib/builtins/fp_lib.h
+++ b/compiler-rt/lib/builtins/fp_lib.h
@@ -58,15 +58,8 @@ typedef double fp_t;
 #define REP_C UINT64_C
 #define significandBits 52
 
-static __inline int rep_clz(rep_t a) {
-#if defined __LP64__
-  return __builtin_clzl(a);
-#else
-  if (a & REP_C(0xffffffff00000000))
-    return clzsi(a >> 32);
-  else
-    return 32 + clzsi(a & REP_C(0xffffffff));
-#endif
+static inline int rep_clz(rep_t a) {
+  return __builtin_clzll(a);
 }
 
 #define loWord(a) (a & 0xffffffffU)