[AArch64] Improve TLS Descriptor pattern to release RTL loop IV opt

The instruction sequences for preparing argument for TLS descriptor
runtime resolver and the later function call to resolver can actually be
hoisted out of the loop.

Currently we can't because we have exposed the hard register X0 as
destination of "set".  While GCC's RTL data flow infrastructure will
skip or do very conservative assumption when hard register involved in
and thus some loop IV opportunities are missed.

This patch add another "tlsdesc_small_pseudo_<mode>" pattern, and avoid
expose x0 to gcc generic code.

Generally, we define a new register class FIXED_R0 which only contains register
0, so the instruction sequences generated from the new add pattern is the same
as tlsdesc_small_<mode>, while the operand 0 is wrapped as pseudo register that
RTL IV opt can handle it.

Ideally, we should allow operand 0 to be any pseudo register, but then
we can't model the override of x0 caused by the function call which is
hidded by the UNSPEC.

So here, we restricting operand 0 to be x0, the override of x0 can be
reflected to the gcc.

2015-08-06    Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
	      Jiong Wang  <jiong.wang@arm.com>
gcc/
  * config/aarch64/aarch64.d (tlsdesc_small_pseudo_<mode>): New pattern.
  * config/aarch64/aarch64.h (reg_class): New enumeration FIXED_REG0.
  (REG_CLASS_NAMES): Likewise.
  (REG_CLASS_CONTENTS): Likewise.
  * config/aarch64/aarch64.c (aarch64_class_max_nregs): Likewise.
  (aarch64_register_move_cost): Likewise.
  (aarch64_load_symref_appropriately): Invoke the new added pattern if
  possible.
  * config/aarch64/constraints.md (Uc0): New constraint.

gcc/testsuite/
  * gcc.target/aarch64/tlsdesc_hoist.c: New testcase.

From-SVN: r226683

5 files changed, 75 insertions, 5 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 795867a..ffcd947 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2015-08-06    Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
+	      Jiong Wang  <jiong.wang@arm.com>
+
+	* config/aarch64/aarch64.d (tlsdesc_small_pseudo_<mode>): New pattern.
+	* config/aarch64/aarch64.h (reg_class): New enumeration FIXED_REG0.
+	(REG_CLASS_NAMES): Likewise.
+	(REG_CLASS_CONTENTS): Likewise.
+	* config/aarch64/aarch64.c (aarch64_class_max_nregs): Likewise.
+	(aarch64_register_move_cost): Likewise.
+	(aarch64_load_symref_appropriately): Invoke the new added pattern if
+	possible.
+	* config/aarch64/constraints.md (Uc0): New constraint.
+
 2015-08-06  Jiong Wang  <jiong.wang@arm.com>
 
 	* config/aarch64/constraints.md (Usf): Add the test of
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index e991a49..6da7245 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -1048,12 +1048,26 @@ aarch64_load_symref_appropriately (rtx dest, rtx imm,
 
 	gcc_assert (mode == Pmode || mode == ptr_mode);
 
-	/* In ILP32, the got entry is always of SImode size.  Unlike
-	   small GOT, the dest is fixed at reg 0.  */
-	if (TARGET_ILP32)
-	  emit_insn (gen_tlsdesc_small_si (imm));
+	if (can_create_pseudo_p ())
+	  {
+	    rtx reg = gen_reg_rtx (mode);
+
+	    if (TARGET_ILP32)
+	      emit_insn (gen_tlsdesc_small_pseudo_si (imm, reg));
+	    else
+	      emit_insn (gen_tlsdesc_small_pseudo_di (imm, reg));
+
+	    emit_use (reg);
+	  }
 	else
-	  emit_insn (gen_tlsdesc_small_di (imm));
+	  {
+	    /* In ILP32, the got entry is always of SImode size.  Unlike
+	       small GOT, the dest is fixed at reg 0.  */
+	    if (TARGET_ILP32)
+	      emit_insn (gen_tlsdesc_small_si (imm));
+	    else
+	      emit_insn (gen_tlsdesc_small_di (imm));
+	  }
 	tp = aarch64_load_tp (NULL);
 
 	if (mode != Pmode)
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 7f99753..5e8f210 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -4549,6 +4549,23 @@
   [(set_attr "type" "call")
    (set_attr "length" "16")])
 
+;; The same as tlsdesc_small_<mode> except that we don't expose hard register X0
+;; as the destination of set as it will cause trouble for RTL loop iv.
+;; RTL loop iv will abort ongoing optimization once it finds there is hard reg
+;; as destination of set.  This pattern thus could help these tlsdesc
+;; instruction sequences hoisted out of loop.
+(define_insn "tlsdesc_small_pseudo_<mode>"
+  [(set (match_operand:PTR 1 "register_operand" "=r")
+        (unspec:PTR [(match_operand 0 "aarch64_valid_symref" "S")]
+		   UNSPEC_TLSDESC))
+   (clobber (reg:DI R0_REGNUM))
+   (clobber (reg:DI LR_REGNUM))
+   (clobber (reg:CC CC_REGNUM))]
+  "TARGET_TLS_DESC"
+  "adrp\\tx0, %A0\;ldr\\t%<w>1, [x0, #%L0]\;add\\t<w>0, <w>0, %L0\;.tlsdesccall\\t%0\;blr\\t%1"
+  [(set_attr "type" "call")
+   (set_attr "length" "16")])
+
 (define_insn "stack_tie"
   [(set (mem:BLK (scratch))
 	(unspec:BLK [(match_operand:DI 0 "register_operand" "rk")
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 0cd004b..0d4937c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,9 @@
 2015-08-06  Jiong Wang  <jiong.wang@arm.com>
 
+	* gcc.target/aarch64/tlsdesc_hoist.c: New testcase.
+
+2015-08-06  Jiong Wang  <jiong.wang@arm.com>
+
 	* gcc.target/aarch64/noplt_3.c: New testcase.
 
 2015-08-06  Jiong Wang  <jiong.wang@arm.com>
diff --git a/gcc/testsuite/gcc.target/aarch64/tlsdesc_hoist.c b/gcc/testsuite/gcc.target/aarch64/tlsdesc_hoist.c
new file mode 100644
index 0000000..a1fd3b0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/tlsdesc_hoist.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target tls_native } */
+/* { dg-options "-O2 -fpic -fdump-rtl-loop2_invariant" } */
+/* { dg-skip-if "-mcmodel=large, no support for -fpic" { aarch64-*-* }  { "-mcmodel=large" } { "" } } */
+
+int cal (int, int);
+__thread int tls_data;
+
+int
+foo (int bound)
+{
+  int i = 0;
+  int sum = 0;
+
+  for (i; i < bound; i++)
+    sum = cal (sum, tls_data);
+
+  return sum;
+}
+
+/* Insn sequences for TLS descriptor should be hoisted out of the loop.  */
+/* { dg-final { scan-rtl-dump "Decided" "loop2_invariant" } } */