Make '-mtune=x86_64' assume fast unaligned memory accesses.

Summary:
Not all chips targeted by x86_64 have this feature, but a dramatically
increasing number do. Specifying a chip-specific tuning parameter will
continue to turn the feature on or off as appropriate for that
particular chip, but the generic flag should try to achieve the best
performance on the most widely available hardware. Today, the number of
chips with fast UA access dwarfs those without in the x86-64 space.

Note that this also brings LLVM's code generation for this '-march' flag
more in line with that of modern GCCs.

CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D195

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169740 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86.td b/lib/Target/X86/X86.td
index e3c22d9c3b8c417c80a23c14659de46529e1561e..b9d8cf76453b72f4873766e4253a8377aef08d5d 100644 (file)
--- a/lib/Target/X86/X86.td
+++ b/lib/Target/X86/X86.td
@@ -155,7 +155,8 @@ def : Proc<"pentium3m",       [FeatureSSE1, FeatureSlowBTMem]>;
 def : Proc<"pentium-m",       [FeatureSSE2, FeatureSlowBTMem]>;
 def : Proc<"pentium4",        [FeatureSSE2]>;
 def : Proc<"pentium4m",       [FeatureSSE2, FeatureSlowBTMem]>;
-def : Proc<"x86-64",          [FeatureSSE2, Feature64Bit, FeatureSlowBTMem]>;
+def : Proc<"x86-64",          [FeatureSSE2, Feature64Bit, FeatureSlowBTMem,
+                               FeatureFastUAMem]>;
 def : Proc<"yonah",           [FeatureSSE3, FeatureSlowBTMem]>;
 def : Proc<"prescott",        [FeatureSSE3, FeatureSlowBTMem]>;
 def : Proc<"nocona",          [FeatureSSE3, FeatureCMPXCHG16B,