Declare lgamma library builtins as never being const

[jgravelle-google]

Summary

POSIX requires lgamma writes to an external global variable, signgam.
This prevents annotating lgamma with readnone, which is incorrect on
targets that write to signgam.

[efriedma]

include/clang/Basic/Builtins.def

1091

Please add a comment explaining why this doesn't have an "e" marking.

[jgravelle-google]

• Add comment to lgamma builtins

[jgravelle-google]

Thanks, added a comment

[hfinkel]

LGTM

include/clang/Basic/Builtins.def

 LIBBUILTIN(hypot, "ddd", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(hypotf, "fff", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(hypotl, "LdLdLd", "fne", "math.h", ALL_LANGUAGES)
 
 LIBBUILTIN(ilogb, "id", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(ilogbf, "if", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(ilogbl, "iLd", "fne", "math.h", ALL_LANGUAGES)
 
-LIBBUILTIN(lgamma, "dd", "fne", "math.h", ALL_LANGUAGES)
-LIBBUILTIN(lgammaf, "ff", "fne", "math.h", ALL_LANGUAGES)
-LIBBUILTIN(lgammal, "LdLd", "fne", "math.h", ALL_LANGUAGES)
+// POSIX math.h declares a global, signgam, that lgamma writes to, so these
+// shouldn't have "e" or "c" attributes
+LIBBUILTIN(lgamma, "dd", "fn", "math.h", ALL_LANGUAGES)
+LIBBUILTIN(lgammaf, "ff", "fn", "math.h", ALL_LANGUAGES)
+LIBBUILTIN(lgammal, "LdLd", "fn", "math.h", ALL_LANGUAGES)
 
 LIBBUILTIN(llrint, "LLid", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(llrintf, "LLif", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(llrintl, "LLiLd", "fne", "math.h", ALL_LANGUAGES)
 
 LIBBUILTIN(llround, "LLid", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(llroundf, "LLif", "fne", "math.h", ALL_LANGUAGES)
 LIBBUILTIN(llroundl, "LLiLd", "fne", "math.h", ALL_LANGUAGES)

test/CodeGen/libcall-declarations.c

 // CHECK-NOERRNO: declare float @fminf(float, float) [[NUW]]
 // CHECK-NOERRNO: declare x86_fp80 @fminl(x86_fp80, x86_fp80) [[NUW]]
 // CHECK-NOERRNO: declare double @hypot(double, double) [[NUW]]
 // CHECK-NOERRNO: declare float @hypotf(float, float) [[NUW]]
 // CHECK-NOERRNO: declare x86_fp80 @hypotl(x86_fp80, x86_fp80) [[NUW]]
 // CHECK-NOERRNO: declare i32 @ilogb(double) [[NUW]]
 // CHECK-NOERRNO: declare i32 @ilogbf(float) [[NUW]]
 // CHECK-NOERRNO: declare i32 @ilogbl(x86_fp80) [[NUW]]
-// CHECK-NOERRNO: declare double @lgamma(double) [[NUW]]
-// CHECK-NOERRNO: declare float @lgammaf(float) [[NUW]]
-// CHECK-NOERRNO: declare x86_fp80 @lgammal(x86_fp80) [[NUW]]
+// CHECK-NOERRNO: declare double @lgamma(double) [[NONCONST:#[0-9]+]]
+// CHECK-NOERRNO: declare float @lgammaf(float) [[NONCONST]]
+// CHECK-NOERRNO: declare x86_fp80 @lgammal(x86_fp80) [[NONCONST]]
 // CHECK-NOERRNO: declare i64 @llrint(double) [[NUW]]
 // CHECK-NOERRNO: declare i64 @llrintf(float) [[NUW]]
 // CHECK-NOERRNO: declare i64 @llrintl(x86_fp80) [[NUW]]
 // CHECK-NOERRNO: declare i64 @llround(double) [[NUW]]
 // CHECK-NOERRNO: declare i64 @llroundf(float) [[NUW]]
 // CHECK-NOERRNO: declare i64 @llroundl(x86_fp80) [[NUW]]
 // CHECK-NOERRNO: declare double @log(double) [[NUW]]
 // CHECK-NOERRNO: declare float @logf(float) [[NUW]]

 // CHECK-ERRNO: declare float @floorf(float) [[NUW]]
 // CHECK-ERRNO: declare x86_fp80 @floorl(x86_fp80) [[NUW]]
 // CHECK-ERRNO: declare double @fmax(double, double) [[NUW]]
 // CHECK-ERRNO: declare float @fmaxf(float, float) [[NUW]]
 // CHECK-ERRNO: declare x86_fp80 @fmaxl(x86_fp80, x86_fp80) [[NUW]]
 // CHECK-ERRNO: declare double @fmin(double, double) [[NUW]]
 // CHECK-ERRNO: declare float @fminf(float, float) [[NUW]]
 // CHECK-ERRNO: declare x86_fp80 @fminl(x86_fp80, x86_fp80) [[NUW]]
+// CHECK-ERRNO: declare double @lgamma(double) [[NONCONST:#[0-9]+]]
+// CHECK-ERRNO: declare float @lgammaf(float) [[NONCONST]]
+// CHECK-ERRNO: declare x86_fp80 @lgammal(x86_fp80) [[NONCONST]]
 // CHECK-ERRNO: declare double @nearbyint(double) [[NUW]]
 // CHECK-ERRNO: declare float @nearbyintf(float) [[NUW]]
 // CHECK-ERRNO: declare x86_fp80 @nearbyintl(x86_fp80) [[NUW]]
 // CHECK-ERRNO: declare double @rint(double) [[NUW]]
 // CHECK-ERRNO: declare float @rintf(float) [[NUW]]
 // CHECK-ERRNO: declare x86_fp80 @rintl(x86_fp80) [[NUW]]
 // CHECK-ERRNO: declare double @round(double) [[NUW]]
 // CHECK-ERRNO: declare float @roundf(float) [[NUW]]

 // CHECK-ERRNO: declare { double, double } @csqrt(double, double) [[NUW]]
 // CHECK-ERRNO: declare <2 x float> @csqrtf(<2 x float>) [[NUW]]
 // CHECK-ERRNO: declare { double, double } @ctan(double, double) [[NUW]]
 // CHECK-ERRNO: declare <2 x float> @ctanf(<2 x float>) [[NUW]]
 // CHECK-ERRNO: declare { double, double } @ctanh(double, double) [[NUW]]
 // CHECK-ERRNO: declare <2 x float> @ctanhf(<2 x float>) [[NUW]]
 
 // CHECK-NOERRNO: attributes [[NUW]] = { nounwind readnone{{.*}} }
+// CHECK-NOERRNO: attributes [[NONCONST]] = {
+// CHECK-NOERRNO-NOT: readnone
+// CHECK-NOERRNO-SAME: nounwind{{.*}} }
 
+// CHECK-ERRNO: attributes [[NONCONST]] = {
+// CHECK-ERRNO-NOT: readnone
+// CHECK-ERRNO-SAME: nounwind{{.*}} }
 // CHECK-ERRNO: attributes [[NUW]] = { nounwind readnone{{.*}} }