[llvm-branch-commits] [libclc] libclc: Invert subnormal checks (PR #187355)

[Matt Arsenault via llvm-branch-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/187355

The base case is correct denormal handling, not flushing. This
also matches the spec controls, which starts at IEEE and
flushing is enabled with -cl-denorms-are-zero.

Also fix wrong defaults for half and double. Denormal support is
not optional for these.

>From cfb1fa05243285cb8ee0eb530fbfb57279bb18d9 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Wed, 18 Mar 2026 18:33:36 +0100
Subject: [PATCH] libclc: Invert subnormal checks

The base case is correct denormal handling, not flushing. This
also matches the spec controls, which starts at IEEE and
flushing is enabled with -cl-denorms-are-zero.

Also fix wrong defaults for half and double. Denormal support is
not optional for these.
---
 libclc/clc/include/clc/math/clc_subnormal_config.h |  7 +++----
 libclc/clc/include/clc/math/math.h                 |  2 +-
 libclc/clc/lib/generic/math/clc_ldexp.cl           |  2 +-
 libclc/clc/lib/generic/subnormal_config.cl         | 14 +++-----------
 4 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/libclc/clc/include/clc/math/clc_subnormal_config.h b/libclc/clc/include/clc/math/clc_subnormal_config.h
index b157720533d72..3b6298e621f0e 100644
--- a/libclc/clc/include/clc/math/clc_subnormal_config.h
+++ b/libclc/clc/include/clc/math/clc_subnormal_config.h
@@ -10,9 +10,8 @@
 
 #include "clc/clcfunc.h"
 
-_CLC_DECL bool __clc_subnormals_disabled();
-_CLC_DECL bool __clc_fp16_subnormals_supported();
-_CLC_DECL bool __clc_fp32_subnormals_supported();
-_CLC_DECL bool __clc_fp64_subnormals_supported();
+_CLC_DECL bool __clc_denormals_are_zero_fp16();
+_CLC_DECL bool __clc_denormals_are_zero_fp32();
+_CLC_DECL bool __clc_denormals_are_zero_fp64();
 
 #endif // __CLC_MATH_CLC_SUBNORMAL_CONFIG_H__
diff --git a/libclc/clc/include/clc/math/math.h b/libclc/clc/include/clc/math/math.h
index f11296bdd00c4..15b1272b37466 100644
--- a/libclc/clc/include/clc/math/math.h
+++ b/libclc/clc/include/clc/math/math.h
@@ -60,7 +60,7 @@
 
 _CLC_OVERLOAD _CLC_INLINE float __clc_flush_denormal_if_not_supported(float x) {
   int ix = __clc_as_int(x);
-  if (!__clc_fp32_subnormals_supported() && ((ix & EXPBITS_SP32) == 0) &&
+  if (__clc_denormals_are_zero_fp32() && ((ix & EXPBITS_SP32) == 0) &&
       ((ix & MANTBITS_SP32) != 0)) {
     ix &= SIGNBIT_SP32;
     x = __clc_as_float(ix);
diff --git a/libclc/clc/lib/generic/math/clc_ldexp.cl b/libclc/clc/lib/generic/math/clc_ldexp.cl
index a2a0e82b7f4e7..59db94cf047fa 100644
--- a/libclc/clc/lib/generic/math/clc_ldexp.cl
+++ b/libclc/clc/lib/generic/math/clc_ldexp.cl
@@ -16,7 +16,7 @@
 
 _CLC_DEF _CLC_OVERLOAD float __clc_ldexp(float x, int n) {
 
-  if (!__clc_fp32_subnormals_supported()) {
+  if (__clc_denormals_are_zero_fp32()) {
     // This treats subnormals as zeros
     int i = __clc_as_int(x);
     int e = (i >> 23) & 0xff;
diff --git a/libclc/clc/lib/generic/subnormal_config.cl b/libclc/clc/lib/generic/subnormal_config.cl
index f3a9ae8deebe9..c80d48802c890 100644
--- a/libclc/clc/lib/generic/subnormal_config.cl
+++ b/libclc/clc/lib/generic/subnormal_config.cl
@@ -8,14 +8,6 @@
 
 #include "clc/math/clc_subnormal_config.h"
 
-_CLC_DEF bool __clc_fp16_subnormals_supported() { return false; }
-
-_CLC_DEF bool __clc_fp32_subnormals_supported() { return false; }
-
-_CLC_DEF bool __clc_fp64_subnormals_supported() {
-#if defined(CLC_SPIRV) || defined(CLC_CLSPV)
-  return false;
-#else
-  return true;
-#endif
-}
+_CLC_DEF bool __clc_denormals_are_zero_fp16() { return false; }
+_CLC_DEF bool __clc_denormals_are_zero_fp32() { return true; }
+_CLC_DEF bool __clc_denormals_are_zero_fp64() { return false; }