spatel created this revision.
spatel added reviewers: gfalcon, lebedev.ri.
Herald added a subscriber: mcrosier.
https://bugs.llvm.org/show_bug.cgi?id=37778
...shows a miscompile resulting from marking nan builtins as 'const'.
The nan libcalls/builtins take a pointer argument:
http://www.cplusplus.com/reference/cmath/nan-function/
...and the chars dereferenced by that arg are used to fill in the NaN constant
payload bits.
"const" means that the pointer argument isn't dereferenced. That's translated
to "readnone" in LLVM.
"pure" means that the pointer argument may be dereferenced. That's translated
to "readonly" in LLVM.
This change prevents the IR optimizer from killing the lead-up to the nan call
here:
double a() {
char buf[4];
buf[0] = buf[1] = buf[2] = '9';
buf[3] = '\0';
return __builtin_nan(buf);
}
...the optimizer isn't currently able to simplify this to a constant as we
might hope, but this patch should solve the miscompile.
https://reviews.llvm.org/D48134
Files:
include/clang/Basic/Builtins.def
test/CodeGen/math-builtins.c
Index: test/CodeGen/math-builtins.c
===================================================================
--- test/CodeGen/math-builtins.c
+++ test/CodeGen/math-builtins.c
@@ -90,25 +90,25 @@
__builtin_nan(c); __builtin_nanf(c); __builtin_nanl(c);
__builtin_nanf128(c);
-// NO__ERRNO: declare double @nan(i8*) [[READNONE]]
-// NO__ERRNO: declare float @nanf(i8*) [[READNONE]]
-// NO__ERRNO: declare x86_fp80 @nanl(i8*) [[READNONE]]
-// NO__ERRNO: declare fp128 @nanf128(i8*) [[READNONE]]
-// HAS_ERRNO: declare double @nan(i8*) [[READNONE:#[0-9]+]]
-// HAS_ERRNO: declare float @nanf(i8*) [[READNONE]]
-// HAS_ERRNO: declare x86_fp80 @nanl(i8*) [[READNONE]]
-// HAS_ERRNO: declare fp128 @nanf128(i8*) [[READNONE]]
+// NO__ERRNO: declare double @nan(i8*) [[PURE:#[0-9]+]]
+// NO__ERRNO: declare float @nanf(i8*) [[PURE]]
+// NO__ERRNO: declare x86_fp80 @nanl(i8*) [[PURE]]
+// NO__ERRNO: declare fp128 @nanf128(i8*) [[PURE]]
+// HAS_ERRNO: declare double @nan(i8*) [[PURE:#[0-9]+]]
+// HAS_ERRNO: declare float @nanf(i8*) [[PURE]]
+// HAS_ERRNO: declare x86_fp80 @nanl(i8*) [[PURE]]
+// HAS_ERRNO: declare fp128 @nanf128(i8*) [[PURE]]
__builtin_nans(c); __builtin_nansf(c); __builtin_nansl(c);
__builtin_nansf128(c);
-// NO__ERRNO: declare double @nans(i8*) [[READNONE]]
-// NO__ERRNO: declare float @nansf(i8*) [[READNONE]]
-// NO__ERRNO: declare x86_fp80 @nansl(i8*) [[READNONE]]
-// NO__ERRNO: declare fp128 @nansf128(i8*) [[READNONE]]
-// HAS_ERRNO: declare double @nans(i8*) [[READNONE]]
-// HAS_ERRNO: declare float @nansf(i8*) [[READNONE]]
-// HAS_ERRNO: declare x86_fp80 @nansl(i8*) [[READNONE]]
-// HAS_ERRNO: declare fp128 @nansf128(i8*) [[READNONE]]
+// NO__ERRNO: declare double @nans(i8*) [[PURE]]
+// NO__ERRNO: declare float @nansf(i8*) [[PURE]]
+// NO__ERRNO: declare x86_fp80 @nansl(i8*) [[PURE]]
+// NO__ERRNO: declare fp128 @nansf128(i8*) [[PURE]]
+// HAS_ERRNO: declare double @nans(i8*) [[PURE]]
+// HAS_ERRNO: declare float @nansf(i8*) [[PURE]]
+// HAS_ERRNO: declare x86_fp80 @nansl(i8*) [[PURE]]
+// HAS_ERRNO: declare fp128 @nansf128(i8*) [[PURE]]
__builtin_pow(f,f); __builtin_powf(f,f); __builtin_powl(f,f);
@@ -188,7 +188,7 @@
// NO__ERRNO: declare double @cbrt(double) [[READNONE]]
// NO__ERRNO: declare float @cbrtf(float) [[READNONE]]
// NO__ERRNO: declare x86_fp80 @cbrtl(x86_fp80) [[READNONE]]
-// HAS_ERRNO: declare double @cbrt(double) [[READNONE]]
+// HAS_ERRNO: declare double @cbrt(double) [[READNONE:#[0-9]+]]
// HAS_ERRNO: declare float @cbrtf(float) [[READNONE]]
// HAS_ERRNO: declare x86_fp80 @cbrtl(x86_fp80) [[READNONE]]
@@ -581,9 +581,11 @@
// NO__ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} }
// NO__ERRNO: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} }
// NO__ERRNO: attributes [[NOT_READNONE]] = { nounwind "correctly{{.*}} }
+// NO__ERRNO: attributes [[PURE]] = { {{.*}}readonly{{.*}} }
// HAS_ERRNO: attributes [[NOT_READNONE]] = { nounwind "correctly{{.*}} }
// HAS_ERRNO: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} }
+// HAS_ERRNO: attributes [[PURE]] = { {{.*}}readonly{{.*}} }
// HAS_ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} }
// HAS_ERRNO_GNU: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} }
Index: include/clang/Basic/Builtins.def
===================================================================
--- include/clang/Basic/Builtins.def
+++ include/clang/Basic/Builtins.def
@@ -137,14 +137,14 @@
BUILTIN(__builtin_modf , "ddd*" , "Fn")
BUILTIN(__builtin_modff, "fff*" , "Fn")
BUILTIN(__builtin_modfl, "LdLdLd*", "Fn")
-BUILTIN(__builtin_nan, "dcC*" , "ncF")
-BUILTIN(__builtin_nanf, "fcC*" , "ncF")
-BUILTIN(__builtin_nanl, "LdcC*", "ncF")
-BUILTIN(__builtin_nanf128, "LLdcC*", "ncF")
-BUILTIN(__builtin_nans, "dcC*" , "ncF")
-BUILTIN(__builtin_nansf, "fcC*" , "ncF")
-BUILTIN(__builtin_nansl, "LdcC*", "ncF")
-BUILTIN(__builtin_nansf128, "LLdcC*", "ncF")
+BUILTIN(__builtin_nan, "dcC*" , "FnU")
+BUILTIN(__builtin_nanf, "fcC*" , "FnU")
+BUILTIN(__builtin_nanl, "LdcC*", "FnU")
+BUILTIN(__builtin_nanf128, "LLdcC*", "FnU")
+BUILTIN(__builtin_nans, "dcC*" , "FnU")
+BUILTIN(__builtin_nansf, "fcC*" , "FnU")
+BUILTIN(__builtin_nansl, "LdcC*", "FnU")
+BUILTIN(__builtin_nansf128, "LLdcC*", "FnU")
BUILTIN(__builtin_powi , "ddi" , "Fnc")
BUILTIN(__builtin_powif, "ffi" , "Fnc")
BUILTIN(__builtin_powil, "LdLdi", "Fnc")
Index: test/CodeGen/math-builtins.c
===================================================================
--- test/CodeGen/math-builtins.c
+++ test/CodeGen/math-builtins.c
@@ -90,25 +90,25 @@
__builtin_nan(c); __builtin_nanf(c); __builtin_nanl(c); __builtin_nanf128(c);
-// NO__ERRNO: declare double @nan(i8*) [[READNONE]]
-// NO__ERRNO: declare float @nanf(i8*) [[READNONE]]
-// NO__ERRNO: declare x86_fp80 @nanl(i8*) [[READNONE]]
-// NO__ERRNO: declare fp128 @nanf128(i8*) [[READNONE]]
-// HAS_ERRNO: declare double @nan(i8*) [[READNONE:#[0-9]+]]
-// HAS_ERRNO: declare float @nanf(i8*) [[READNONE]]
-// HAS_ERRNO: declare x86_fp80 @nanl(i8*) [[READNONE]]
-// HAS_ERRNO: declare fp128 @nanf128(i8*) [[READNONE]]
+// NO__ERRNO: declare double @nan(i8*) [[PURE:#[0-9]+]]
+// NO__ERRNO: declare float @nanf(i8*) [[PURE]]
+// NO__ERRNO: declare x86_fp80 @nanl(i8*) [[PURE]]
+// NO__ERRNO: declare fp128 @nanf128(i8*) [[PURE]]
+// HAS_ERRNO: declare double @nan(i8*) [[PURE:#[0-9]+]]
+// HAS_ERRNO: declare float @nanf(i8*) [[PURE]]
+// HAS_ERRNO: declare x86_fp80 @nanl(i8*) [[PURE]]
+// HAS_ERRNO: declare fp128 @nanf128(i8*) [[PURE]]
__builtin_nans(c); __builtin_nansf(c); __builtin_nansl(c); __builtin_nansf128(c);
-// NO__ERRNO: declare double @nans(i8*) [[READNONE]]
-// NO__ERRNO: declare float @nansf(i8*) [[READNONE]]
-// NO__ERRNO: declare x86_fp80 @nansl(i8*) [[READNONE]]
-// NO__ERRNO: declare fp128 @nansf128(i8*) [[READNONE]]
-// HAS_ERRNO: declare double @nans(i8*) [[READNONE]]
-// HAS_ERRNO: declare float @nansf(i8*) [[READNONE]]
-// HAS_ERRNO: declare x86_fp80 @nansl(i8*) [[READNONE]]
-// HAS_ERRNO: declare fp128 @nansf128(i8*) [[READNONE]]
+// NO__ERRNO: declare double @nans(i8*) [[PURE]]
+// NO__ERRNO: declare float @nansf(i8*) [[PURE]]
+// NO__ERRNO: declare x86_fp80 @nansl(i8*) [[PURE]]
+// NO__ERRNO: declare fp128 @nansf128(i8*) [[PURE]]
+// HAS_ERRNO: declare double @nans(i8*) [[PURE]]
+// HAS_ERRNO: declare float @nansf(i8*) [[PURE]]
+// HAS_ERRNO: declare x86_fp80 @nansl(i8*) [[PURE]]
+// HAS_ERRNO: declare fp128 @nansf128(i8*) [[PURE]]
__builtin_pow(f,f); __builtin_powf(f,f); __builtin_powl(f,f);
@@ -188,7 +188,7 @@
// NO__ERRNO: declare double @cbrt(double) [[READNONE]]
// NO__ERRNO: declare float @cbrtf(float) [[READNONE]]
// NO__ERRNO: declare x86_fp80 @cbrtl(x86_fp80) [[READNONE]]
-// HAS_ERRNO: declare double @cbrt(double) [[READNONE]]
+// HAS_ERRNO: declare double @cbrt(double) [[READNONE:#[0-9]+]]
// HAS_ERRNO: declare float @cbrtf(float) [[READNONE]]
// HAS_ERRNO: declare x86_fp80 @cbrtl(x86_fp80) [[READNONE]]
@@ -581,9 +581,11 @@
// NO__ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} }
// NO__ERRNO: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} }
// NO__ERRNO: attributes [[NOT_READNONE]] = { nounwind "correctly{{.*}} }
+// NO__ERRNO: attributes [[PURE]] = { {{.*}}readonly{{.*}} }
// HAS_ERRNO: attributes [[NOT_READNONE]] = { nounwind "correctly{{.*}} }
// HAS_ERRNO: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} }
+// HAS_ERRNO: attributes [[PURE]] = { {{.*}}readonly{{.*}} }
// HAS_ERRNO: attributes [[READNONE]] = { {{.*}}readnone{{.*}} }
// HAS_ERRNO_GNU: attributes [[READNONE_INTRINSIC]] = { {{.*}}readnone{{.*}} }
Index: include/clang/Basic/Builtins.def
===================================================================
--- include/clang/Basic/Builtins.def
+++ include/clang/Basic/Builtins.def
@@ -137,14 +137,14 @@
BUILTIN(__builtin_modf , "ddd*" , "Fn")
BUILTIN(__builtin_modff, "fff*" , "Fn")
BUILTIN(__builtin_modfl, "LdLdLd*", "Fn")
-BUILTIN(__builtin_nan, "dcC*" , "ncF")
-BUILTIN(__builtin_nanf, "fcC*" , "ncF")
-BUILTIN(__builtin_nanl, "LdcC*", "ncF")
-BUILTIN(__builtin_nanf128, "LLdcC*", "ncF")
-BUILTIN(__builtin_nans, "dcC*" , "ncF")
-BUILTIN(__builtin_nansf, "fcC*" , "ncF")
-BUILTIN(__builtin_nansl, "LdcC*", "ncF")
-BUILTIN(__builtin_nansf128, "LLdcC*", "ncF")
+BUILTIN(__builtin_nan, "dcC*" , "FnU")
+BUILTIN(__builtin_nanf, "fcC*" , "FnU")
+BUILTIN(__builtin_nanl, "LdcC*", "FnU")
+BUILTIN(__builtin_nanf128, "LLdcC*", "FnU")
+BUILTIN(__builtin_nans, "dcC*" , "FnU")
+BUILTIN(__builtin_nansf, "fcC*" , "FnU")
+BUILTIN(__builtin_nansl, "LdcC*", "FnU")
+BUILTIN(__builtin_nansf128, "LLdcC*", "FnU")
BUILTIN(__builtin_powi , "ddi" , "Fnc")
BUILTIN(__builtin_powif, "ffi" , "Fnc")
BUILTIN(__builtin_powil, "LdLdi", "Fnc")
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