From 0be02ef5b1eeb1dd2e8adc1bcbeb4183d4b7304e Mon Sep 17 00:00:00 2001
From: Sanjay Patel <spatel@rotateright.com>
Date: Tue, 17 Feb 2015 22:09:54 +0000
Subject: [PATCH] Add comment to explain a non-obvious setting; NFC.
This is paraphrased from Simon Pilgrim's comment in:
http://reviews.llvm.org/D7492
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229566 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Target/X86/X86InstrInfo.cpp | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 65f8b74d95c..88e454aa0cf 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -657,6 +657,12 @@ X86InstrInfo::X86InstrInfo(X86Subtarget &STI)
{ X86::VTESTPSYrr, X86::VTESTPSYrm, 0 },
// AVX2 foldable instructions
+
+ // 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.
{ X86::VBROADCASTSSrr, X86::VBROADCASTSSrm, TB_NO_REVERSE },
{ X86::VBROADCASTSSYrr, X86::VBROADCASTSSYrm, TB_NO_REVERSE },
{ X86::VBROADCASTSDYrr, X86::VBROADCASTSDYrm, TB_NO_REVERSE },