path: root/arch
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authorMarius Hillenbrand <>2020-12-01 15:36:34 +0100
committerRich Felker <>2020-12-03 19:07:24 -0500
commit738c4e945c1218559d36b83cbaba11459fad89c9 (patch)
tree58c66e2603b4c9c0ebde61ea79f6cf8dece07261 /arch
parent821083ac7b54eaa040d5a8ddc67c6206a175e0ca (diff)
s390x: derive float_t from compiler or default to float
float_t should represent the type that is used to evaluate float expressions internally. On s390x, float_t is currently set to double. In contrast, the isa supports single-precision float operations and compilers by default evaluate float in single precision, which violates the C standard (sections and 7.12 in C11/C17, to be precise). With -fexcess-precision=standard, gcc evaluates float in double precision, which aligns with the standard yet at the cost of added conversion instructions. gcc-11 will drop the special case to retrofit double precision behavior for -fexcess-precision=standard so that __FLT_EVAL_METHOD__ will be 0 on s390x in any scenario. To improve standards compliance and compatibility with future compiler direction, this patch changes the definition of float_t to be derived from the compiler's __FLT_EVAL_METHOD__.
Diffstat (limited to 'arch')
2 files changed, 9 insertions, 1 deletions
diff --git a/arch/s390x/bits/ b/arch/s390x/bits/
index 15d18c8f..6c0eb7f4 100644
--- a/arch/s390x/bits/
+++ b/arch/s390x/bits/
@@ -9,7 +9,11 @@
TYPEDEF int wchar_t;
+#if defined(__FLT_EVAL_METHOD__) && __FLT_EVAL_METHOD__ == 1
TYPEDEF double float_t;
+TYPEDEF float float_t;
TYPEDEF double double_t;
TYPEDEF struct { long long __ll; long double __ld; } max_align_t;
diff --git a/arch/s390x/bits/float.h b/arch/s390x/bits/float.h
index 90b73bee..e188cb61 100644
--- a/arch/s390x/bits/float.h
+++ b/arch/s390x/bits/float.h
@@ -1,4 +1,8 @@
-#define FLT_EVAL_METHOD 1
+#ifdef __FLT_EVAL_METHOD__
+#define FLT_EVAL_METHOD 0
#define LDBL_TRUE_MIN 6.47517511943802511092443895822764655e-4966L
#define LDBL_MIN 3.36210314311209350626267781732175260e-4932L