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authorThiago Macieira <thiago.macieira@intel.com>2015-02-10 22:19:51 -0800
committerThiago Macieira <thiago.macieira@intel.com>2015-02-17 00:42:04 +0000
commitb584648df169bb9c8b67b24b4504b0fea82b093d (patch)
tree8506080a4bb82de5b9a82c6a33a932f8daef8bf2 /src/corelib/global
parent738e9b185c72b6814bc3e4ea2a7a23adce326a73 (diff)
Use Clang 3.6's __builtin_assume in Q_ASSUME
It's more efficient than the current implementation. Example: int f(int i) { Q_ASSUME(i < 8); return i < 8; } Before: cmpl $8, %edi setl %al movzbl %al, %eax retq After: movl $1, %eax retq Change-Id: I1a800c709d3543699131ffff13c1c50713a8da2c Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com> Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Diffstat (limited to 'src/corelib/global')
-rw-r--r--src/corelib/global/qcompilerdetection.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/src/corelib/global/qcompilerdetection.h b/src/corelib/global/qcompilerdetection.h
index 8ef8b79902..ba87bb5cc9 100644
--- a/src/corelib/global/qcompilerdetection.h
+++ b/src/corelib/global/qcompilerdetection.h
@@ -173,7 +173,11 @@
# else
# define Q_CC_CLANG ((__clang_major__ * 100) + __clang_minor__)
# endif
-# define Q_ASSUME_IMPL(expr) if (expr){} else __builtin_unreachable()
+# if __has_builtin(__builtin_assume)
+# define Q_ASSUME_IMPL(expr) __builtin_assume(expr)
+# else
+# define Q_ASSUME_IMPL(expr) if (expr){} else __builtin_unreachable()
+# endif
# define Q_UNREACHABLE_IMPL() __builtin_unreachable()
# if !defined(__has_extension)
# /* Compatibility with older Clang versions */