HIP: Use builtin_nan instead of manual expansion

[arsenm]

I'm guessing the only reason the __make_mantissa* functions
exist were to support this, so maybe these can be deleted now.

This is broken in the non-constant string case, since it ends
up emitting a call to the libm function

[arsenm]

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• HIP: Use builtin_nan instead of manual expansion #128023 👈 (View in Graphite)
• clang/HIP: Remove some unused ocml function declarations #128022
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[llvmbot]

@llvm/pr-subscribers-backend-x86

@llvm/pr-subscribers-clang

Author: Matt Arsenault (arsenm)

Changes

I'm guessing the only reason the __make_mantissa* functions
exist were to support this, so maybe these can be deleted now.

This is broken in the non-constant string case, since it ends
up emitting a call to the libm function

---

Full diff: https://github.com/llvm/llvm-project/pull/128023.diff

1 Files Affected:

• (modified) clang/lib/Headers/__clang_hip_math.h (+3-42)

diff --git a/clang/lib/Headers/__clang_hip_math.h b/clang/lib/Headers/__clang_hip_math.h
index 79cb7906852c4..8c21f5d882181 100644
--- a/clang/lib/Headers/__clang_hip_math.h
+++ b/clang/lib/Headers/__clang_hip_math.h
@@ -519,24 +519,8 @@ float modff(float __x, float *__iptr) {
 }
 
 __DEVICE__
-float nanf(const char *__tagp __attribute__((nonnull))) {
-  union {
-    float val;
-    struct ieee_float {
-      unsigned int mantissa : 22;
-      unsigned int quiet : 1;
-      unsigned int exponent : 8;
-      unsigned int sign : 1;
-    } bits;
-  } __tmp;
-  __static_assert_type_size_equal(sizeof(__tmp.val), sizeof(__tmp.bits));
-
-  __tmp.bits.sign = 0u;
-  __tmp.bits.exponent = ~0u;
-  __tmp.bits.quiet = 1u;
-  __tmp.bits.mantissa = __make_mantissa(__tagp);
-
-  return __tmp.val;
+float nanf(const char *__tagp) {
+  return __builtin_nanf(__tagp);
 }
 
 __DEVICE__
@@ -1072,30 +1056,7 @@ double modf(double __x, double *__iptr) {
 
 __DEVICE__
 double nan(const char *__tagp) {
-#if !_WIN32
-  union {
-    double val;
-    struct ieee_double {
-      uint64_t mantissa : 51;
-      uint32_t quiet : 1;
-      uint32_t exponent : 11;
-      uint32_t sign : 1;
-    } bits;
-  } __tmp;
-  __static_assert_type_size_equal(sizeof(__tmp.val), sizeof(__tmp.bits));
-
-  __tmp.bits.sign = 0u;
-  __tmp.bits.exponent = ~0u;
-  __tmp.bits.quiet = 1u;
-  __tmp.bits.mantissa = __make_mantissa(__tagp);
-
-  return __tmp.val;
-#else
-  __static_assert_type_size_equal(sizeof(uint64_t), sizeof(double));
-  uint64_t __val = __make_mantissa(__tagp);
-  __val |= 0xFFF << 51;
-  return *reinterpret_cast<double *>(&__val);
-#endif
+  return __builtin_nan(__tagp);
 }
 
 __DEVICE__

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff c6c75b5d7a9a1869bfcdc413a98b00fe4b9f07d1 88b441975bc452c5b19d30b4d534fbce0b16dc0b --extensions h -- clang/lib/Headers/__clang_hip_math.h

View the diff from clang-format here.

diff --git a/clang/lib/Headers/__clang_hip_math.h b/clang/lib/Headers/__clang_hip_math.h
index 8c21f5d882..1f62a06b50 100644
--- a/clang/lib/Headers/__clang_hip_math.h
+++ b/clang/lib/Headers/__clang_hip_math.h
@@ -519,9 +519,7 @@ float modff(float __x, float *__iptr) {
 }
 
 __DEVICE__
-float nanf(const char *__tagp) {
-  return __builtin_nanf(__tagp);
-}
+float nanf(const char *__tagp) { return __builtin_nanf(__tagp); }
 
 __DEVICE__
 float nearbyintf(float __x) { return __builtin_nearbyintf(__x); }
@@ -1055,9 +1053,7 @@ double modf(double __x, double *__iptr) {
 }
 
 __DEVICE__
-double nan(const char *__tagp) {
-  return __builtin_nan(__tagp);
-}
+double nan(const char *__tagp) { return __builtin_nan(__tagp); }
 
 __DEVICE__
 double nearbyint(double __x) { return __builtin_nearbyint(__x); }

[yxsamliu]

why do we want to do this if it is broken for non-literal string?

[b-sumner]

why do we want to do this if it is broken for non-literal string?

Right. It doesn't seem likely that it won't be literal, but no documentation I've found requires it to be.

[arsenm]

why do we want to do this if it is broken for non-literal string?

It's WIP from 3 years ago, I'm putting this up for reference