[gcc r12-6764] arm: add basic mitigation for Cortex-A AES errata

[Richard Earnshaw]

https://gcc.gnu.org/g:bc13384e1956a9bc38b084f82e250743451aae61

commit r12-6764-gbc13384e1956a9bc38b084f82e250743451aae61
Author: Richard Earnshaw <rearnsha@arm.com>
Date:   Thu Oct 21 17:29:41 2021 +0100

    arm: add basic mitigation for Cortex-A AES errata
    
    This patch adds the basic patterns for mitigation of the erratum, but no
    attempt is made at this point to optimize the results for the cases where
    the erratum mitigation is not needed.
    
    The mitigation is done by guaranteeing that the input operands are fed
    from a full-width operation by using an identity operation on the input
    values.
    
    gcc/ChangeLog:
    
            * config/arm/crypto.md (crypto_<CRYPTO_AES:crypto_pattern>): Convert
            to define_expand.  Add mitigation for the Cortex-A AES erratum
            when enabled.
            (*crypto_<CRYPTO_AES:crypto_pattern>_insn): New pattern, based
            on original crypto_<CRYPTO_AES:crypto_pattern> insn.
            (aes_op_protect): New pattern.
            * config/arm/unspecs.md (unspec): Add UNSPEC_AES_PROTECT.

Diff:
---
 gcc/config/arm/crypto.md  | 36 +++++++++++++++++++++++++++++++++++-
 gcc/config/arm/unspecs.md |  1 +
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/gcc/config/arm/crypto.md b/gcc/config/arm/crypto.md
index 020dfba7dcf..fbee1829ce8 100644
--- a/gcc/config/arm/crypto.md
+++ b/gcc/config/arm/crypto.md
@@ -29,7 +29,28 @@
   [(set_attr "type" "<crypto_type>")]
 )
 
-(define_insn "crypto_<CRYPTO_AES:crypto_pattern>"
+(define_expand "crypto_<CRYPTO_AES:crypto_pattern>"
+  [(set (match_operand:<crypto_mode> 0 "register_operand" "=w")
+	(unspec:<crypto_mode>
+		[(xor:<crypto_mode>
+		     (match_operand:<crypto_mode> 1 "register_operand" "%0")
+		     (match_operand:<crypto_mode> 2 "register_operand" "w"))]
+	CRYPTO_AES))]
+  "TARGET_CRYPTO"
+{
+  if (fix_aes_erratum_1742098)
+    {
+      rtx op1_protect = gen_reg_rtx (V16QImode);
+      emit_insn (gen_aes_op_protect (op1_protect, operands[1]));
+      operands[1] = op1_protect;
+      rtx op2_protect = gen_reg_rtx (V16QImode);
+      emit_insn (gen_aes_op_protect (op2_protect, operands[2]));
+      operands[2] = op2_protect;
+    }
+  /* Fall through to default expansion.  */
+})
+
+(define_insn "*crypto_<CRYPTO_AES:crypto_pattern>_insn"
   [(set (match_operand:<crypto_mode> 0 "register_operand" "=w")
 	(unspec:<crypto_mode>
 	 [(xor:<crypto_mode>
@@ -41,6 +62,19 @@
   [(set_attr "type" "<crypto_type>")]
 )
 
+; Mitigate against AES erratum on Cortex-A57 and Cortex-A72 by performing
+; a 128-bit operation on an operand producer.  This can be eliminated only
+; if we know that the operand was produced by a full-width operation.
+; V16QImode matches <crypto_mode> for the AES instructions.
+(define_insn "aes_op_protect"
+  [(set (match_operand:V16QI 0 "register_operand" "=w")
+	(unspec:V16QI [(match_operand:V16QI 1 "register_operand" "0")]
+	 UNSPEC_AES_PROTECT))]
+  "TARGET_CRYPTO && fix_aes_erratum_1742098"
+  "vmov\\t%q0, %q1"
+  [(set_attr "type" "neon_move_q")]
+)
+
 ;; When AESE/AESMC fusion is enabled we really want to keep the two together
 ;; and enforce the register dependency without scheduling or register
 ;; allocation messing up the order or introducing moves inbetween.
diff --git a/gcc/config/arm/unspecs.md b/gcc/config/arm/unspecs.md
index 2782af08834..7748e784379 100644
--- a/gcc/config/arm/unspecs.md
+++ b/gcc/config/arm/unspecs.md
@@ -270,6 +270,7 @@
   UNSPEC_AESE
   UNSPEC_AESIMC
   UNSPEC_AESMC
+  UNSPEC_AES_PROTECT
   UNSPEC_SHA1C
   UNSPEC_SHA1M
   UNSPEC_SHA1P