[llvm] r334758 - [X86] Fix stale comment in folding tables.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Thu Jun 14 12:28:31 2018
New Revision: 334758

URL: http://llvm.org/viewvc/llvm-project?rev=334758&view=rev
Log:
[X86] Fix stale comment in folding tables.

Modified:
    llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=334758&r1=334757&r2=334758&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Thu Jun 14 12:28:31 2018
@@ -805,9 +805,9 @@ X86InstrInfo::X86InstrInfo(X86Subtarget
 
     // VBROADCASTS{SD}rr register instructions were an AVX2 addition while the
     // VBROADCASTS{SD}rm memory instructions were available from AVX1.
-    // TB_NO_REVERSE prevents unfolding from introducing an illegal instruction
-    // on AVX1 targets. The VPBROADCAST instructions are all AVX2 instructions
-    // so they don't need an equivalent limitation.
+    // TB_NO_REVERSE prevents unfolding because doing so would create a full
+    // vector load while the broadcast load would have only been a single
+    // element.
     { X86::VBROADCASTSSrr,  X86::VBROADCASTSSrm,      TB_NO_REVERSE },
     { X86::VBROADCASTSSYrr, X86::VBROADCASTSSYrm,     TB_NO_REVERSE },
     { X86::VBROADCASTSDYrr, X86::VBROADCASTSDYrm,     TB_NO_REVERSE },