[x86] invert logic for attribute 'FeatureFastUAMem'

This is a 'no functional change intended' patch. It removes one FIXME, but adds several more.

Motivation: the FeatureFastUAMem attribute may be too general. It is used to determine if any
sized misaligned memory access under 32-bytes is 'fast'. From the added FIXME comments, however,
you can see that we're not consistent about this. Changing the name of the attribute makes it
clearer to see the logic holes.

Changing this to a 'slow' attribute also means we don't have to add an explicit 'fast' attribute
to new chips; fast unaligned accesses have been standard for several generations of CPUs now.

Differential Revision: http://reviews.llvm.org/D12154

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245729 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86.td b/lib/Target/X86/X86.td
index 7c2a0c0..d081614 100644 (file)
--- a/lib/Target/X86/X86.td
+++ b/lib/Target/X86/X86.td
@@ -79,16 +79,12 @@ def FeatureSlowBTMem : SubtargetFeature<"slow-bt-mem", "IsBTMemSlow", "true",
                                        "Bit testing of memory is slow">;
 def FeatureSlowSHLD : SubtargetFeature<"slow-shld", "IsSHLDSlow", "true",
                                        "SHLD instruction is slow">;
-// FIXME: This is a 16-byte (SSE/AVX) feature; we should rename it to make that
-// explicit. Also, it seems this would be the default state for most chips
-// going forward, so it would probably be better to negate the logic and
-// match the 32-byte "slow mem" feature below.
-def FeatureFastUAMem : SubtargetFeature<"fast-unaligned-mem",
-                                        "IsUAMemFast", "true",
-                                        "Fast unaligned memory access">;
+def FeatureSlowUAMem : SubtargetFeature<"slow-unaligned-mem-under-32",
+                                "IsUAMemUnder32Slow", "true",
+                                "Slow unaligned 16-byte-or-less memory access">;
 def FeatureSlowUAMem32 : SubtargetFeature<"slow-unaligned-mem-32",
-                            "IsUAMem32Slow", "true",
-                            "Slow unaligned 32-byte memory access">;
+                                "IsUAMem32Slow", "true",
+                                "Slow unaligned 32-byte memory access">;
 def FeatureSSE4A   : SubtargetFeature<"sse4a", "HasSSE4A", "true",
                                       "Support SSE 4a instructions",
                                       [FeatureSSE3]>;
@@ -213,38 +209,42 @@ def ProcIntelSLM  : SubtargetFeature<"slm", "X86ProcFamily", "IntelSLM",
 class Proc<string Name, list<SubtargetFeature> Features>
  : ProcessorModel<Name, GenericModel, Features>;
 
-def : Proc<"generic",         []>;
-def : Proc<"i386",            []>;
-def : Proc<"i486",            []>;
-def : Proc<"i586",            []>;
-def : Proc<"pentium",         []>;
-def : Proc<"pentium-mmx",     [FeatureMMX]>;
-def : Proc<"i686",            []>;
-def : Proc<"pentiumpro",      [FeatureCMOV]>;
-def : Proc<"pentium2",        [FeatureMMX, FeatureCMOV]>;
-def : Proc<"pentium3",        [FeatureSSE1]>;
-def : Proc<"pentium3m",       [FeatureSSE1, FeatureSlowBTMem]>;
-def : Proc<"pentium-m",       [FeatureSSE2, FeatureSlowBTMem]>;
-def : Proc<"pentium4",        [FeatureSSE2]>;
-def : Proc<"pentium4m",       [FeatureSSE2, FeatureSlowBTMem]>;
+def : Proc<"generic",         [FeatureSlowUAMem]>;
+def : Proc<"i386",            [FeatureSlowUAMem]>;
+def : Proc<"i486",            [FeatureSlowUAMem]>;
+def : Proc<"i586",            [FeatureSlowUAMem]>;
+def : Proc<"pentium",         [FeatureSlowUAMem]>;
+def : Proc<"pentium-mmx",     [FeatureSlowUAMem, FeatureMMX]>;
+def : Proc<"i686",            [FeatureSlowUAMem]>;
+def : Proc<"pentiumpro",      [FeatureSlowUAMem, FeatureCMOV]>;
+def : Proc<"pentium2",        [FeatureSlowUAMem, FeatureMMX, FeatureCMOV]>;
+def : Proc<"pentium3",        [FeatureSlowUAMem, FeatureSSE1]>;
+def : Proc<"pentium3m",       [FeatureSlowUAMem, FeatureSSE1, FeatureSlowBTMem]>;
+def : Proc<"pentium-m",       [FeatureSlowUAMem, FeatureSSE2, FeatureSlowBTMem]>;
+def : Proc<"pentium4",        [FeatureSlowUAMem, FeatureSSE2]>;
+def : Proc<"pentium4m",       [FeatureSlowUAMem, FeatureSSE2, FeatureSlowBTMem]>;
 
 // Intel Core Duo.
 def : ProcessorModel<"yonah", SandyBridgeModel,
-                     [FeatureSSE3, FeatureSlowBTMem]>;
+                     [FeatureSlowUAMem, FeatureSSE3, FeatureSlowBTMem]>;
 
 // NetBurst.
-def : Proc<"prescott", [FeatureSSE3, FeatureSlowBTMem]>;
-def : Proc<"nocona",   [FeatureSSE3, FeatureCMPXCHG16B, FeatureSlowBTMem]>;
+def : Proc<"prescott", [FeatureSlowUAMem, FeatureSSE3, FeatureSlowBTMem]>;
+def : Proc<"nocona",   [FeatureSlowUAMem, FeatureSSE3, FeatureCMPXCHG16B,
+                        FeatureSlowBTMem]>;
 
 // Intel Core 2 Solo/Duo.
 def : ProcessorModel<"core2", SandyBridgeModel,
-                     [FeatureSSSE3, FeatureCMPXCHG16B, FeatureSlowBTMem]>;
+                     [FeatureSlowUAMem, FeatureSSSE3, FeatureCMPXCHG16B,
+                      FeatureSlowBTMem]>;
 def : ProcessorModel<"penryn", SandyBridgeModel,
-                     [FeatureSSE41, FeatureCMPXCHG16B, FeatureSlowBTMem]>;
+                     [FeatureSlowUAMem, FeatureSSE41, FeatureCMPXCHG16B,
+                      FeatureSlowBTMem]>;
 
 // Atom CPUs.
 class BonnellProc<string Name> : ProcessorModel<Name, AtomModel, [
                                    ProcIntelAtom,
+                                   FeatureSlowUAMem,
                                    FeatureSSSE3,
                                    FeatureCMPXCHG16B,
                                    FeatureMOVBE,
@@ -272,8 +272,7 @@ class SilvermontProc<string Name> : ProcessorModel<Name, SLMModel, [
                                       FeaturePRFCHW,
                                       FeatureSlowLEA,
                                       FeatureSlowIncDec,
-                                      FeatureSlowBTMem,
-                                      FeatureFastUAMem
+                                      FeatureSlowBTMem
                                     ]>;
 def : SilvermontProc<"silvermont">;
 def : SilvermontProc<"slm">; // Legacy alias.
@@ -283,7 +282,6 @@ class NehalemProc<string Name> : ProcessorModel<Name, SandyBridgeModel, [
                                    FeatureSSE42,
                                    FeatureCMPXCHG16B,
                                    FeatureSlowBTMem,
-                                   FeatureFastUAMem,
                                    FeaturePOPCNT
                                  ]>;
 def : NehalemProc<"nehalem">;
@@ -295,7 +293,6 @@ class WestmereProc<string Name> : ProcessorModel<Name, SandyBridgeModel, [
                                     FeatureSSE42,
                                     FeatureCMPXCHG16B,
                                     FeatureSlowBTMem,
-                                    FeatureFastUAMem,
                                     FeaturePOPCNT,
                                     FeatureAES,
                                     FeaturePCLMUL
@@ -308,7 +305,6 @@ class SandyBridgeProc<string Name> : ProcessorModel<Name, SandyBridgeModel, [
                                        FeatureAVX,
                                        FeatureCMPXCHG16B,
                                        FeatureSlowBTMem,
-                                       FeatureFastUAMem,
                                        FeatureSlowUAMem32,
                                        FeaturePOPCNT,
                                        FeatureAES,
@@ -321,7 +317,6 @@ class IvyBridgeProc<string Name> : ProcessorModel<Name, SandyBridgeModel, [
                                      FeatureAVX,
                                      FeatureCMPXCHG16B,
                                      FeatureSlowBTMem,
-                                     FeatureFastUAMem,
                                      FeatureSlowUAMem32,
                                      FeaturePOPCNT,
                                      FeatureAES,
@@ -337,7 +332,6 @@ class HaswellProc<string Name> : ProcessorModel<Name, HaswellModel, [
                                    FeatureAVX2,
                                    FeatureCMPXCHG16B,
                                    FeatureSlowBTMem,
-                                   FeatureFastUAMem,
                                    FeaturePOPCNT,
                                    FeatureAES,
                                    FeaturePCLMUL,
@@ -360,7 +354,6 @@ class BroadwellProc<string Name> : ProcessorModel<Name, HaswellModel, [
                                      FeatureAVX2,
                                      FeatureCMPXCHG16B,
                                      FeatureSlowBTMem,
-                                     FeatureFastUAMem,
                                      FeaturePOPCNT,
                                      FeatureAES,
                                      FeaturePCLMUL,
@@ -383,7 +376,7 @@ def : BroadwellProc<"broadwell">;
 // FIXME: define KNL model
 class KnightsLandingProc<string Name> : ProcessorModel<Name, HaswellModel,
                      [FeatureAVX512, FeatureERI, FeatureCDI, FeaturePFI,
-                      FeatureCMPXCHG16B, FeatureFastUAMem, FeaturePOPCNT,
+                      FeatureCMPXCHG16B, FeaturePOPCNT,
                       FeatureAES, FeaturePCLMUL, FeatureRDRAND, FeatureF16C,
                       FeatureFSGSBase, FeatureMOVBE, FeatureLZCNT, FeatureBMI,
                       FeatureBMI2, FeatureFMA, FeatureRTM, FeatureHLE,
@@ -394,7 +387,7 @@ def : KnightsLandingProc<"knl">;
 class SkylakeProc<string Name> : ProcessorModel<Name, HaswellModel,
                      [FeatureAVX512, FeatureCDI,
                       FeatureDQI, FeatureBWI, FeatureVLX,
-                      FeatureCMPXCHG16B, FeatureSlowBTMem, FeatureFastUAMem,
+                      FeatureCMPXCHG16B, FeatureSlowBTMem,
                       FeaturePOPCNT, FeatureAES, FeaturePCLMUL, FeatureRDRAND,
                       FeatureF16C, FeatureFSGSBase, FeatureMOVBE, FeatureLZCNT,
                       FeatureBMI, FeatureBMI2, FeatureFMA, FeatureRTM,
@@ -406,67 +399,77 @@ def : SkylakeProc<"skx">; // Legacy alias.
 
 // AMD CPUs.
 
-def : Proc<"k6",              [FeatureMMX]>;
-def : Proc<"k6-2",            [Feature3DNow]>;
-def : Proc<"k6-3",            [Feature3DNow]>;
-def : Proc<"athlon",          [Feature3DNowA, FeatureSlowBTMem,
-                               FeatureSlowSHLD]>;
-def : Proc<"athlon-tbird",    [Feature3DNowA, FeatureSlowBTMem,
-                               FeatureSlowSHLD]>;
-def : Proc<"athlon-4",        [FeatureSSE1,   Feature3DNowA, FeatureSlowBTMem,
-                               FeatureSlowSHLD]>;
-def : Proc<"athlon-xp",       [FeatureSSE1,   Feature3DNowA, FeatureSlowBTMem,
-                               FeatureSlowSHLD]>;
-def : Proc<"athlon-mp",       [FeatureSSE1,   Feature3DNowA, FeatureSlowBTMem,
-                               FeatureSlowSHLD]>;
-def : Proc<"k8",              [FeatureSSE2,   Feature3DNowA, Feature64Bit,
+def : Proc<"k6",              [FeatureSlowUAMem, FeatureMMX]>;
+def : Proc<"k6-2",            [FeatureSlowUAMem, Feature3DNow]>;
+def : Proc<"k6-3",            [FeatureSlowUAMem, Feature3DNow]>;
+def : Proc<"athlon",          [FeatureSlowUAMem, Feature3DNowA,
                                FeatureSlowBTMem, FeatureSlowSHLD]>;
-def : Proc<"opteron",         [FeatureSSE2,   Feature3DNowA, Feature64Bit,
+def : Proc<"athlon-tbird",    [FeatureSlowUAMem, Feature3DNowA,
                                FeatureSlowBTMem, FeatureSlowSHLD]>;
-def : Proc<"athlon64",        [FeatureSSE2,   Feature3DNowA, Feature64Bit,
+def : Proc<"athlon-4",        [FeatureSlowUAMem, FeatureSSE1, Feature3DNowA,
                                FeatureSlowBTMem, FeatureSlowSHLD]>;
-def : Proc<"athlon-fx",       [FeatureSSE2,   Feature3DNowA, Feature64Bit,
+def : Proc<"athlon-xp",       [FeatureSlowUAMem, FeatureSSE1, Feature3DNowA,
                                FeatureSlowBTMem, FeatureSlowSHLD]>;
-def : Proc<"k8-sse3",         [FeatureSSE3,   Feature3DNowA, FeatureCMPXCHG16B,
+def : Proc<"athlon-mp",       [FeatureSlowUAMem, FeatureSSE1, Feature3DNowA,
                                FeatureSlowBTMem, FeatureSlowSHLD]>;
-def : Proc<"opteron-sse3",    [FeatureSSE3,   Feature3DNowA, FeatureCMPXCHG16B,
-                               FeatureSlowBTMem, FeatureSlowSHLD]>;
-def : Proc<"athlon64-sse3",   [FeatureSSE3,   Feature3DNowA, FeatureCMPXCHG16B,
-                               FeatureSlowBTMem, FeatureSlowSHLD]>;
-def : Proc<"amdfam10",        [FeatureSSE4A,
+def : Proc<"k8",              [FeatureSlowUAMem, FeatureSSE2, Feature3DNowA,
+                               Feature64Bit, FeatureSlowBTMem,
+                               FeatureSlowSHLD]>;
+def : Proc<"opteron",         [FeatureSlowUAMem, FeatureSSE2, Feature3DNowA,
+                               Feature64Bit, FeatureSlowBTMem,
+                               FeatureSlowSHLD]>;
+def : Proc<"athlon64",        [FeatureSlowUAMem, FeatureSSE2,   Feature3DNowA,
+                               Feature64Bit, FeatureSlowBTMem,
+                               FeatureSlowSHLD]>;
+def : Proc<"athlon-fx",       [FeatureSlowUAMem, FeatureSSE2,   Feature3DNowA,
+                               Feature64Bit, FeatureSlowBTMem,
+                               FeatureSlowSHLD]>;
+def : Proc<"k8-sse3",         [FeatureSlowUAMem, FeatureSSE3,   Feature3DNowA,
+                               FeatureCMPXCHG16B, FeatureSlowBTMem,
+                               FeatureSlowSHLD]>;
+def : Proc<"opteron-sse3",    [FeatureSlowUAMem, FeatureSSE3,   Feature3DNowA,
+                               FeatureCMPXCHG16B, FeatureSlowBTMem,
+                               FeatureSlowSHLD]>;
+def : Proc<"athlon64-sse3",   [FeatureSlowUAMem, FeatureSSE3,   Feature3DNowA,
+                               FeatureCMPXCHG16B, FeatureSlowBTMem,
+                               FeatureSlowSHLD]>;
+def : Proc<"amdfam10",        [FeatureSlowUAMem, FeatureSSE4A,
                                Feature3DNowA, FeatureCMPXCHG16B, FeatureLZCNT,
                                FeaturePOPCNT, FeatureSlowBTMem,
                                FeatureSlowSHLD]>;
-def : Proc<"barcelona",       [FeatureSSE4A,
+def : Proc<"barcelona",       [FeatureSlowUAMem, FeatureSSE4A,
                                Feature3DNowA, FeatureCMPXCHG16B, FeatureLZCNT,
                                FeaturePOPCNT, FeatureSlowBTMem,
                                FeatureSlowSHLD]>;
+
+// FIXME: We should remove 'FeatureSlowUAMem' from AMD chips under here.
+
 // Bobcat
 def : Proc<"btver1",          [FeatureSSSE3, FeatureSSE4A, FeatureCMPXCHG16B,
                                FeaturePRFCHW, FeatureLZCNT, FeaturePOPCNT,
-                               FeatureSlowSHLD]>;
+                               FeatureSlowSHLD, FeatureSlowUAMem]>;
 
 // Jaguar
 def : ProcessorModel<"btver2", BtVer2Model,
                      [FeatureAVX, FeatureSSE4A, FeatureCMPXCHG16B,
                       FeaturePRFCHW, FeatureAES, FeaturePCLMUL,
                       FeatureBMI, FeatureF16C, FeatureMOVBE,
-                      FeatureLZCNT, FeaturePOPCNT, FeatureFastUAMem,
+                      FeatureLZCNT, FeaturePOPCNT,
                       FeatureSlowSHLD]>;
 
-// TODO: We should probably add 'FeatureFastUAMem' to all of the AMD chips.
-
 // Bulldozer
 def : Proc<"bdver1",          [FeatureXOP, FeatureFMA4, FeatureCMPXCHG16B,
                                FeatureAES, FeaturePRFCHW, FeaturePCLMUL,
                                FeatureAVX, FeatureSSE4A, FeatureLZCNT,
-                               FeaturePOPCNT, FeatureSlowSHLD]>;
+                               FeaturePOPCNT, FeatureSlowSHLD,
+                               FeatureSlowUAMem]>;
 // Piledriver
 def : Proc<"bdver2",          [FeatureXOP, FeatureFMA4, FeatureCMPXCHG16B,
                                FeatureAES, FeaturePRFCHW, FeaturePCLMUL,
                                FeatureAVX, FeatureSSE4A, FeatureF16C,
                                FeatureLZCNT, FeaturePOPCNT, FeatureBMI,
-                               FeatureTBM, FeatureFMA, FeatureSlowSHLD]>;
+                               FeatureTBM, FeatureFMA, FeatureSlowSHLD,
+                               FeatureSlowUAMem]>;
 
 // Steamroller
 def : Proc<"bdver3",          [FeatureXOP, FeatureFMA4, FeatureCMPXCHG16B,
@@ -474,7 +477,7 @@ def : Proc<"bdver3",          [FeatureXOP, FeatureFMA4, FeatureCMPXCHG16B,
                                FeatureAVX, FeatureSSE4A, FeatureF16C,
                                FeatureLZCNT, FeaturePOPCNT, FeatureBMI,
                                FeatureTBM, FeatureFMA, FeatureSlowSHLD,
-                               FeatureFSGSBase]>;
+                               FeatureFSGSBase, FeatureSlowUAMem]>;
 
 // Excavator
 def : Proc<"bdver4",          [FeatureAVX2, FeatureXOP, FeatureFMA4,
@@ -482,14 +485,14 @@ def : Proc<"bdver4",          [FeatureAVX2, FeatureXOP, FeatureFMA4,
                                FeaturePCLMUL, FeatureF16C, FeatureLZCNT,
                                FeaturePOPCNT, FeatureBMI, FeatureBMI2,
                                FeatureTBM, FeatureFMA, FeatureSSE4A,
-                               FeatureFSGSBase]>;
+                               FeatureFSGSBase, FeatureSlowUAMem]>;
 
-def : Proc<"geode",           [Feature3DNowA]>;
+def : Proc<"geode",           [FeatureSlowUAMem, Feature3DNowA]>;
 
-def : Proc<"winchip-c6",      [FeatureMMX]>;
-def : Proc<"winchip2",        [Feature3DNow]>;
-def : Proc<"c3",              [Feature3DNow]>;
-def : Proc<"c3-2",            [FeatureSSE1]>;
+def : Proc<"winchip-c6",      [FeatureSlowUAMem, FeatureMMX]>;
+def : Proc<"winchip2",        [FeatureSlowUAMem, Feature3DNow]>;
+def : Proc<"c3",              [FeatureSlowUAMem, Feature3DNow]>;
+def : Proc<"c3-2",            [FeatureSlowUAMem, FeatureSSE1]>;
 
 // We also provide a generic 64-bit specific x86 processor model which tries to
 // be good for modern chips without enabling instruction set encodings past the
@@ -502,8 +505,7 @@ def : Proc<"c3-2",            [FeatureSSE1]>;
 // knobs which need to be tuned differently for AMD chips, we might consider
 // forming a common base for them.
 def : ProcessorModel<"x86-64", SandyBridgeModel,
-                     [FeatureSSE2, Feature64Bit, FeatureSlowBTMem,
-                      FeatureFastUAMem]>;
+                     [FeatureSSE2, Feature64Bit, FeatureSlowBTMem]>;
 
 //===----------------------------------------------------------------------===//
 // Register File Description

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 9f1bf6d..430ee22 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1876,10 +1876,11 @@ X86TargetLowering::getOptimalMemOpType(uint64_t Size,
   if ((!IsMemset || ZeroMemset) &&
       !F->hasFnAttribute(Attribute::NoImplicitFloat)) {
     if (Size >= 16 &&
-        (Subtarget->isUnalignedMemAccessFast() ||
+        (!Subtarget->isUnalignedMemUnder32Slow() ||
          ((DstAlign == 0 || DstAlign >= 16) &&
           (SrcAlign == 0 || SrcAlign >= 16)))) {
       if (Size >= 32) {
+        // FIXME: Check if unaligned 32-byte accesses are slow.
         if (Subtarget->hasInt256())
           return MVT::v8i32;
         if (Subtarget->hasFp256())
@@ -1897,6 +1898,9 @@ X86TargetLowering::getOptimalMemOpType(uint64_t Size,
       return MVT::f64;
     }
   }
+  // This is a compromise. If we reach here, unaligned accesses may be slow on
+  // this target. However, creating smaller, aligned accesses could be even
+  // slower and would certainly be a lot more code.
   if (Subtarget->is64Bit() && Size >= 8)
     return MVT::i64;
   return MVT::i32;
@@ -1916,12 +1920,10 @@ X86TargetLowering::allowsMisalignedMemoryAccesses(EVT VT,
                                                   unsigned,
                                                   bool *Fast) const {
   if (Fast) {
-    // FIXME: We should be checking 128-bit accesses separately from smaller
-    // accesses.
     if (VT.getSizeInBits() == 256)
       *Fast = !Subtarget->isUnalignedMem32Slow();
     else
-      *Fast = Subtarget->isUnalignedMemAccessFast();
+      *Fast = !Subtarget->isUnalignedMemUnder32Slow();
   }
   return true;
 }

diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index d964bf1..9d799d8 100644 (file)
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -5508,9 +5508,10 @@ bool X86InstrInfo::unfoldMemoryOperand(MachineFunction &MF, MachineInstr *MI,
 
   const MCInstrDesc &MCID = get(Opc);
   const TargetRegisterClass *RC = getRegClass(MCID, Index, &RI, MF);
+  // TODO: Check if 32-byte or greater accesses are slow too?
   if (!MI->hasOneMemOperand() &&
       RC == &X86::VR128RegClass &&
-      !Subtarget.isUnalignedMemAccessFast())
+      Subtarget.isUnalignedMemUnder32Slow())
     // Without memoperands, loadRegFromAddr and storeRegToStackSlot will
     // conservatively assume the address is unaligned. That's bad for
     // performance.
@@ -5658,9 +5659,11 @@ X86InstrInfo::unfoldMemoryOperand(SelectionDAG &DAG, SDNode *N,
                             cast<MachineSDNode>(N)->memoperands_end());
     if (!(*MMOs.first) &&
         RC == &X86::VR128RegClass &&
-        !Subtarget.isUnalignedMemAccessFast())
+        Subtarget.isUnalignedMemUnder32Slow())
       // Do not introduce a slow unaligned load.
       return false;
+    // FIXME: If a VR128 can have size 32, we should be checking if a 32-byte
+    // memory access is slow above.
     unsigned Alignment = RC->getSize() == 32 ? 32 : 16;
     bool isAligned = (*MMOs.first) &&
                      (*MMOs.first)->getAlignment() >= Alignment;
@@ -5701,9 +5704,11 @@ X86InstrInfo::unfoldMemoryOperand(SelectionDAG &DAG, SDNode *N,
                              cast<MachineSDNode>(N)->memoperands_end());
     if (!(*MMOs.first) &&
         RC == &X86::VR128RegClass &&
-        !Subtarget.isUnalignedMemAccessFast())
+        Subtarget.isUnalignedMemUnder32Slow())
       // Do not introduce a slow unaligned store.
       return false;
+    // FIXME: If a VR128 can have size 32, we should be checking if a 32-byte
+    // memory access is slow above.
     unsigned Alignment = RC->getSize() == 32 ? 32 : 16;
     bool isAligned = (*MMOs.first) &&
                      (*MMOs.first)->getAlignment() >= Alignment;

diff --git a/lib/Target/X86/X86Subtarget.cpp b/lib/Target/X86/X86Subtarget.cpp
index c3f686d..565ba1d 100644 (file)
--- a/lib/Target/X86/X86Subtarget.cpp
+++ b/lib/Target/X86/X86Subtarget.cpp
@@ -255,7 +255,7 @@ void X86Subtarget::initializeEnvironment() {
   HasMPX = false;
   IsBTMemSlow = false;
   IsSHLDSlow = false;
-  IsUAMemFast = false;
+  IsUAMemUnder32Slow = false;
   IsUAMem32Slow = false;
   HasSSEUnalignedMem = false;
   HasCmpxchg16b = false;

diff --git a/lib/Target/X86/X86Subtarget.h b/lib/Target/X86/X86Subtarget.h
index 14e0088..d5d0027 100644 (file)
--- a/lib/Target/X86/X86Subtarget.h
+++ b/lib/Target/X86/X86Subtarget.h
@@ -146,10 +146,10 @@ protected:
   /// True if SHLD instructions are slow.
   bool IsSHLDSlow;
 
-  /// True if unaligned memory access is fast.
-  bool IsUAMemFast;
+  /// True if unaligned memory accesses of 16-bytes or smaller are slow.
+  bool IsUAMemUnder32Slow;
 
-  /// True if unaligned 32-byte memory accesses are slow.
+  /// True if unaligned memory accesses of 32-bytes are slow.
   bool IsUAMem32Slow;
 
   /// True if SSE operations can have unaligned memory operands.
@@ -357,7 +357,7 @@ public:
   bool hasRDSEED() const { return HasRDSEED; }
   bool isBTMemSlow() const { return IsBTMemSlow; }
   bool isSHLDSlow() const { return IsSHLDSlow; }
-  bool isUnalignedMemAccessFast() const { return IsUAMemFast; }
+  bool isUnalignedMemUnder32Slow() const { return IsUAMemUnder32Slow; }
   bool isUnalignedMem32Slow() const { return IsUAMem32Slow; }
   bool hasSSEUnalignedMem() const { return HasSSEUnalignedMem; }
   bool hasCmpxchg16b() const { return HasCmpxchg16b; }