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[TLI] Add support for nan libfunc #101356

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Merged
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Jul 31, 2024
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[TLI] Add support for nan libfunc #101356

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15 changes: 15 additions & 0 deletions llvm/include/llvm/Analysis/TargetLibraryInfo.def
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Expand Up @@ -1807,6 +1807,21 @@ TLI_DEFINE_ENUM_INTERNAL(modfl)
TLI_DEFINE_STRING_INTERNAL("modfl")
TLI_DEFINE_SIG_INTERNAL(LDbl, LDbl, Ptr)

/// double nan(const char *arg);
TLI_DEFINE_ENUM_INTERNAL(nan)
TLI_DEFINE_STRING_INTERNAL("nan")
TLI_DEFINE_SIG_INTERNAL(Dbl, Ptr)

/// float nanf(const char *arg);
TLI_DEFINE_ENUM_INTERNAL(nanf)
TLI_DEFINE_STRING_INTERNAL("nanf")
TLI_DEFINE_SIG_INTERNAL(Flt, Ptr)

/// long double nanl(const char *arg);
TLI_DEFINE_ENUM_INTERNAL(nanl)
TLI_DEFINE_STRING_INTERNAL("nanl")
TLI_DEFINE_SIG_INTERNAL(LDbl, Ptr)

/// double nearbyint(double x);
TLI_DEFINE_ENUM_INTERNAL(nearbyint)
TLI_DEFINE_STRING_INTERNAL("nearbyint")
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3 changes: 3 additions & 0 deletions llvm/lib/Transforms/Utils/BuildLibCalls.cpp
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Expand Up @@ -279,6 +279,9 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
Changed |= setNonLazyBind(F);

switch (TheLibFunc) {
case LibFunc_nan:
case LibFunc_nanf:
case LibFunc_nanl:
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Is this correct? These are spec'd to call strtod and friends, which set errno.

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Error handling
This function is not subject to any of the error conditions specified in math_errhandling.

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LLVM's libc implementation sets errno: https://github.com/llvm/llvm-project/pull/76690/files

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glibc also sets errno.

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Is this correct? These are spec'd to call strtod and friends, which set errno.

In this case, strtoX never sets ERANGE. So it looks ok.

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#include <math.h>
#include <errno.h>
#include <stdio.h>

int main() {
	errno = 0;
	double d = nan("99999999999999999999999999999999999999999");
	int err = errno;
	printf("%d %f\n", err, d);
	return 0;
}

$ clang -lm test.c && ./a.out 
34 nan

With glibc. Is this a glibc bug?

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The conditions where strtod would hit an error shouldn't apply for nan though?

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strotod says for NaN sequences:

A character sequence NAN or NAN(n-char-sequenceopt) is interpreted as a quiet NaN, if supported in the return type, else like a subject sequence part that does not have the expected form; the meaning of the n-char sequence
is implementation-defined.

It gives explicit rules for overflow and underflow, which can set errno values, but is silent on what happens with the n-char sequence being out of range of the payload, outside of the above quote. But... there's not really any latitude I see in the specification for errno to be set (unless you think 7.12.1 applies to nan and sNaN is a domain error).

glibc fails because it's using strtoull here, and strtoull does ERANGE on overflow. But I think this is a glibc bug, it shouldn't be setting errno.

(I'm not fully conversant in llvm-libc implementation, but I think the llvm-libc implementation doesn't ever set errno in nan--the interface allows it to, but nothing appears to set an error).

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I filed a glibc bug here: https://sourceware.org/bugzilla/show_bug.cgi?id=32045

case LibFunc_strlen:
case LibFunc_strnlen:
case LibFunc_wcslen:
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11 changes: 10 additions & 1 deletion llvm/test/Transforms/InferFunctionAttrs/annotate.ll
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Expand Up @@ -717,6 +717,15 @@ declare float @modff(float, ptr)
; CHECK: declare x86_fp80 @modfl(x86_fp80, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
declare x86_fp80 @modfl(x86_fp80, ptr)

; CHECK: declare double @nan(ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY_WILLRETURN:#[0-9]+]]
declare double @nan(ptr)

; CHECK: declare float @nanf(ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY_WILLRETURN]]
declare float @nanf(ptr)

; CHECK: declare x86_fp80 @nanl(ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY_WILLRETURN]]
declare x86_fp80 @nanl(ptr)

; CHECK: declare double @nearbyint(double) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
declare double @nearbyint(double)

Expand Down Expand Up @@ -956,7 +965,7 @@ declare ptr @strncpy(ptr, ptr, i64)
; CHECK: declare noalias ptr @strndup(ptr nocapture readonly, i64 noundef) [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND_WILLRETURN_FAMILY_MALLOC]]
declare ptr @strndup(ptr, i64)

; CHECK: declare i64 @strnlen(ptr nocapture, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY_WILLRETURN:#[0-9]+]]
; CHECK: declare i64 @strnlen(ptr nocapture, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY_WILLRETURN]]
declare i64 @strnlen(ptr, i64)

; CHECK: declare ptr @strpbrk(ptr, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY_WILLRETURN]]
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20 changes: 16 additions & 4 deletions llvm/test/tools/llvm-tli-checker/ps4-tli-check.yaml
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Expand Up @@ -34,21 +34,21 @@
#
# CHECK: << Total TLI yes SDK no: 8
# CHECK: >> Total TLI no SDK yes: 0
# CHECK: == Total TLI yes SDK yes: 245
# CHECK: == Total TLI yes SDK yes: 248
#
# WRONG_DETAIL: << TLI yes SDK no : '_ZdaPv' aka operator delete[](void*)
# WRONG_DETAIL: >> TLI no SDK yes: '_ZdaPvj' aka operator delete[](void*, unsigned int)
# WRONG_DETAIL-COUNT-8: << TLI yes SDK no : {{.*}}__hot_cold_t
# WRONG_SUMMARY: << Total TLI yes SDK no: 9{{$}}
# WRONG_SUMMARY: >> Total TLI no SDK yes: 1{{$}}
# WRONG_SUMMARY: == Total TLI yes SDK yes: 244
# WRONG_SUMMARY: == Total TLI yes SDK yes: 247
#
## The -COUNT suffix doesn't care if there are too many matches, so check
## the exact count first; the two directives should add up to that.
## Yes, this means additions to TLI will fail this test, but the argument
## to -COUNT can't be an expression.
# AVAIL: TLI knows 486 symbols, 253 available
# AVAIL-COUNT-253: {{^}} available
# AVAIL: TLI knows 489 symbols, 256 available
# AVAIL-COUNT-256: {{^}} available
# AVAIL-NOT: {{^}} available
# UNAVAIL-COUNT-233: not available
# UNAVAIL-NOT: not available
Expand Down Expand Up @@ -703,6 +703,18 @@ DynamicSymbols:
Type: STT_FUNC
Section: .text
Binding: STB_GLOBAL
- Name: nan
Type: STT_FUNC
Section: .text
Binding: STB_GLOBAL
- Name: nanf
Type: STT_FUNC
Section: .text
Binding: STB_GLOBAL
- Name: nanl
Type: STT_FUNC
Section: .text
Binding: STB_GLOBAL
- Name: nearbyint
Type: STT_FUNC
Section: .text
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3 changes: 3 additions & 0 deletions llvm/unittests/Analysis/TargetLibraryInfoTest.cpp
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Expand Up @@ -255,6 +255,9 @@ TEST_F(TargetLibraryInfoTest, ValidProto) {
"declare double @modf(double, double*)\n"
"declare float @modff(float, float*)\n"
"declare x86_fp80 @modfl(x86_fp80, x86_fp80*)\n"
"declare double @nan(ptr)\n"
"declare float @nanf(ptr)\n"
"declare x86_fp80 @nanl(ptr)\n"
"declare double @nearbyint(double)\n"
"declare float @nearbyintf(float)\n"
"declare x86_fp80 @nearbyintl(x86_fp80)\n"
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