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Re: [PATCH, ARM 6/7, ping1] Add support for CB(N)Z and (U|S)DIV to ARMv8-M Baseline
- From: Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>
- To: Thomas Preudhomme <thomas dot preudhomme at foss dot arm dot com>, Richard Earnshaw <Richard dot Earnshaw at arm dot com>, Ramana Radhakrishnan <ramana dot radhakrishnan at arm dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 20 May 2016 14:22:48 +0100
- Subject: Re: [PATCH, ARM 6/7, ping1] Add support for CB(N)Z and (U|S)DIV to ARMv8-M Baseline
- Authentication-results: sourceware.org; auth=none
- References: <004601d138a3$6e832c10$4b898430$ at foss dot arm dot com> <2666765 dot UAfDCUe3Qi at e108577-lin>
Hi Thomas,
On 17/05/16 11:14, Thomas Preudhomme wrote:
Ping?
*** gcc/ChangeLog ***
2015-11-13 Thomas Preud'homme <thomas.preudhomme@arm.com>
* config/arm/arm.c (arm_print_operand_punct_valid_p): Make %? valid
for Thumb-1.
* config/arm/arm.h (TARGET_HAVE_CBZ): Define.
(TARGET_IDIV): Set for all Thumb targets provided they have hardware
divide feature.
* config/arm/thumb1.md (thumb1_cbz): New insn.
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index
f42e996e5a7ce979fe406b8261d50fb2ba005f6b..347b5b0a5cc0bc1e3b5020c8124d968e76ce48a4
100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -271,9 +271,12 @@ extern void (*arm_lang_output_object_attributes_hook)
(void);
/* Nonzero if this chip provides the movw and movt instructions. */
#define TARGET_HAVE_MOVT (arm_arch_thumb2 || arm_arch8)
+/* Nonzero if this chip provides the cb{n}z instruction. */
+#define TARGET_HAVE_CBZ (arm_arch_thumb2 || arm_arch8)
+
/* Nonzero if integer division instructions supported. */
#define TARGET_IDIV ((TARGET_ARM && arm_arch_arm_hwdiv) \
- || (TARGET_THUMB2 && arm_arch_thumb_hwdiv))
+ || (TARGET_THUMB && arm_arch_thumb_hwdiv))
/* Nonzero if disallow volatile memory access in IT block. */
#define TARGET_NO_VOLATILE_CE (arm_arch_no_volatile_ce)
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index
13b4b71ac8f9c1da8ef1945f7ff6985ca59f6832..445972ce0e3fd27d4411840ff69e9edbb23994fc
100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -22684,7 +22684,7 @@ arm_print_operand_punct_valid_p (unsigned char code)
{
return (code == '@' || code == '|' || code == '.'
|| code == '(' || code == ')' || code == '#'
- || (TARGET_32BIT && (code == '?'))
+ || code == '?'
|| (TARGET_THUMB2 && (code == '!'))
|| (TARGET_THUMB && (code == '_')));
}
Hmm, I'm not a fan of this change. arm_print_operand_punct_valid_p is an implementation
of a target hook that is used to validate user-provided inline asm as well and is therefore
the right place to reject such invalid constructs.
This is just working around the fact that the output template for the [u]divsi3 patterns
has a '%?' in it that is illegal in Thumb1 and will not be used for ARMv8-M Baseline anyway.
I'd prefer it if you add a second alternative to those patterns and emit
the sdiv/udiv mnemonic without the '%?' and enable that for the v8mb arch attribute
(and mark the existing alternative as requiring the "32" arch attribute).
diff --git a/gcc/config/arm/thumb1.md b/gcc/config/arm/thumb1.md
index
4572456b8bc98503061846cad94bc642943db3a2..1b01ef6ce731fe3ff37c3d8c048fb9d5e7829b35
100644
--- a/gcc/config/arm/thumb1.md
+++ b/gcc/config/arm/thumb1.md
@@ -973,6 +973,92 @@
DONE;
})
+;; A pattern for the cb(n)z instruction added in ARMv8-M baseline profile,
+;; adapted from cbranchsi4_insn. Modifying cbranchsi4_insn instead leads to
+;; code generation difference for ARMv6-M because the minimum length of the
+;; instruction becomes 2 even for it due to a limitation in genattrtab's
+;; handling of pc in the length condition.
+(define_insn "thumb1_cbz"
+ [(set (pc) (if_then_else
+ (match_operator 0 "equality_operator"
+ [(match_operand:SI 1 "s_register_operand" "l")
+ (const_int 0)])
+ (label_ref (match_operand 2 "" ""))
+ (pc)))]
+ "TARGET_THUMB1 && TARGET_HAVE_MOVT"
+{
s/TARGET_HAVE_MOVT/TARGET_HAVE_CBZ/
+ if (get_attr_length (insn) == 2)
+ {
+ if (GET_CODE (operands[0]) == EQ)
+ return "cbz\t%1, %l2";
+ else
+ return "cbnz\t%1, %l2";
+ }
+ else
+ {
+ rtx t = cfun->machine->thumb1_cc_insn;
+ if (t != NULL_RTX)
+ {
+ if (!rtx_equal_p (cfun->machine->thumb1_cc_op0, operands[1])
+ || !rtx_equal_p (cfun->machine->thumb1_cc_op1, operands[2]))
+ t = NULL_RTX;
+ if (cfun->machine->thumb1_cc_mode == CC_NOOVmode)
+ {
+ if (!noov_comparison_operator (operands[0], VOIDmode))
+ t = NULL_RTX;
+ }
+ else if (cfun->machine->thumb1_cc_mode != CCmode)
+ t = NULL_RTX;
+ }
+ if (t == NULL_RTX)
+ {
+ output_asm_insn ("cmp\t%1, #0", operands);
+ cfun->machine->thumb1_cc_insn = insn;
+ cfun->machine->thumb1_cc_op0 = operands[1];
+ cfun->machine->thumb1_cc_op1 = operands[2];
+ cfun->machine->thumb1_cc_mode = CCmode;
+ }
+ else
+ /* Ensure we emit the right type of condition code on the jump. */
+ XEXP (operands[0], 0) = gen_rtx_REG (cfun->machine->thumb1_cc_mode,
+ CC_REGNUM);
+
+ switch (get_attr_length (insn))
+ {
+ case 4: return "b%d0\t%l2";
+ case 6: return "b%D0\t.LCB%=;b\t%l2\t%@long jump\n.LCB%=:";
+ case 8: return "b%D0\t.LCB%=;bl\t%l2\t%@far jump\n.LCB%=:";
+ default: gcc_unreachable ();
+ }
+ }
+}
+ [(set (attr "far_jump")
+ (if_then_else
+ (eq_attr "length" "8")
+ (const_string "yes")
+ (const_string "no")))
+ (set (attr "length")
+ (if_then_else
+ (and (ge (minus (match_dup 2) (pc)) (const_int 2))
+ (le (minus (match_dup 2) (pc)) (const_int 128))
+ (not (match_test "which_alternative")))
This pattern only has one alternative so "which_alternative"
will always be 0, so the (not (match_test "which_alternative"))
test inside the 'and' is redundant and can be removed.
Thanks,
Kyrill
+ (const_int 2)
+ (if_then_else
+ (and (ge (minus (match_dup 2) (pc)) (const_int -250))
+ (le (minus (match_dup 2) (pc)) (const_int 256)))
+ (const_int 4)
+ (if_then_else
+ (and (ge (minus (match_dup 2) (pc)) (const_int -2040))
+ (le (minus (match_dup 2) (pc)) (const_int 2048)))
+ (const_int 6)
+ (const_int 8)))))
+ (set (attr "type")
+ (if_then_else
+ (eq_attr "length" "2")
+ (const_string "branch")
+ (const_string "multiple")))]
+)
+
(define_insn "cbranchsi4_insn"
[(set (pc) (if_then_else
(match_operator 0 "arm_comparison_operator"
Best regards,
Thomas
On Thursday 17 December 2015 16:17:52 Thomas Preud'homme wrote:
Hi,
This patch is part of a patch series to add support for ARMv8-M[1] to GCC.
This specific patch makes the compiler start generating code with the new
CB(N)Z and (U|S)DIV instructions for ARMv8-M Baseline.
Sharing of instruction patterns for div insn template with ARM or Thumb-2
was done by allowing %? punctuation character for Thumb-1. This is safe to
do since the compiler would fault in arm_print_condition if a condition
code is not handled by a branch in Thumb1.
Unfortunately, cbz cannot be shared with cbranchsi4 because it would lead to
worse code for Thumb-1. Indeed, choosing cb(n)z over the other alternatives
for cbranchsi4 depends on the distance between target and pc which lead
insn-attrtab to evaluate the minimum length of this pattern to be 2 as it
cannot computer the distance statically. It would be possible to determine
that this alternative is not available for non ARMv8-M Thumb-1 target
statically but genattrtab is not currently capable to do it, so this is for
a later patch.
[1] For a quick overview of ARMv8-M please refer to the initial cover
letter.
ChangeLog entry is as follows:
*** gcc/ChangeLog ***
2015-11-13 Thomas Preud'homme <thomas.preudhomme@arm.com>
* config/arm/arm.c (arm_print_operand_punct_valid_p): Make %? valid
for Thumb-1.
* config/arm/arm.h (TARGET_HAVE_CBZ): Define.
(TARGET_IDIV): Set for all Thumb targets provided they have hardware
divide feature.
* config/arm/thumb1.md (thumb1_cbz): New insn.
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index 015df50..247f144 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -263,9 +263,12 @@ extern void
(*arm_lang_output_object_attributes_hook)(void); /* Nonzero if this chip
provides the movw and movt instructions. */ #define
TARGET_HAVE_MOVT (arm_arch_thumb2 || arm_arch8)
+/* Nonzero if this chip provides the cb{n}z instruction. */
+#define TARGET_HAVE_CBZ (arm_arch_thumb2 || arm_arch8)
+
/* Nonzero if integer division instructions supported. */
#define TARGET_IDIV ((TARGET_ARM && arm_arch_arm_hwdiv) \
- || (TARGET_THUMB2 && arm_arch_thumb_hwdiv))
+ || (TARGET_THUMB && arm_arch_thumb_hwdiv))
/* Nonzero if disallow volatile memory access in IT block. */
#define TARGET_NO_VOLATILE_CE (arm_arch_no_volatile_ce)
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index d832309..5ef3a1d 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -22568,7 +22568,7 @@ arm_print_operand_punct_valid_p (unsigned char code)
{
return (code == '@' || code == '|' || code == '.'
|| code == '(' || code == ')' || code == '#'
- || (TARGET_32BIT && (code == '?'))
+ || code == '?'
|| (TARGET_THUMB2 && (code == '!'))
|| (TARGET_THUMB && (code == '_')));
}
diff --git a/gcc/config/arm/thumb1.md b/gcc/config/arm/thumb1.md
index 7e3bcb4..074b267 100644
--- a/gcc/config/arm/thumb1.md
+++ b/gcc/config/arm/thumb1.md
@@ -973,6 +973,92 @@
DONE;
})
+;; A pattern for the cb(n)z instruction added in ARMv8-M baseline profile,
+;; adapted from cbranchsi4_insn. Modifying cbranchsi4_insn instead leads
to +;; code generation difference for ARMv6-M because the minimum length of
the +;; instruction becomes 2 even for it due to a limitation in
genattrtab's +;; handling of pc in the length condition.
+(define_insn "thumb1_cbz"
+ [(set (pc) (if_then_else
+ (match_operator 0 "equality_operator"
+ [(match_operand:SI 1 "s_register_operand" "l")
+ (const_int 0)])
+ (label_ref (match_operand 2 "" ""))
+ (pc)))]
+ "TARGET_THUMB1 && TARGET_HAVE_MOVT"
+{
+ if (get_attr_length (insn) == 2)
+ {
+ if (GET_CODE (operands[0]) == EQ)
+ return "cbz\t%1, %l2";
+ else
+ return "cbnz\t%1, %l2";
+ }
+ else
+ {
+ rtx t = cfun->machine->thumb1_cc_insn;
+ if (t != NULL_RTX)
+ {
+ if (!rtx_equal_p (cfun->machine->thumb1_cc_op0, operands[1])
+ || !rtx_equal_p (cfun->machine->thumb1_cc_op1, operands[2]))
+ t = NULL_RTX;
+ if (cfun->machine->thumb1_cc_mode == CC_NOOVmode)
+ {
+ if (!noov_comparison_operator (operands[0], VOIDmode))
+ t = NULL_RTX;
+ }
+ else if (cfun->machine->thumb1_cc_mode != CCmode)
+ t = NULL_RTX;
+ }
+ if (t == NULL_RTX)
+ {
+ output_asm_insn ("cmp\t%1, #0", operands);
+ cfun->machine->thumb1_cc_insn = insn;
+ cfun->machine->thumb1_cc_op0 = operands[1];
+ cfun->machine->thumb1_cc_op1 = operands[2];
+ cfun->machine->thumb1_cc_mode = CCmode;
+ }
+ else
+ /* Ensure we emit the right type of condition code on the jump. */
+ XEXP (operands[0], 0) = gen_rtx_REG (cfun->machine->thumb1_cc_mode,
+ CC_REGNUM);
+
+ switch (get_attr_length (insn))
+ {
+ case 4: return "b%d0\t%l2";
+ case 6: return "b%D0\t.LCB%=;b\t%l2\t%@long jump\n.LCB%=:";
+ case 8: return "b%D0\t.LCB%=;bl\t%l2\t%@far jump\n.LCB%=:";
+ default: gcc_unreachable ();
+ }
+ }
+}
+ [(set (attr "far_jump")
+ (if_then_else
+ (eq_attr "length" "8")
+ (const_string "yes")
+ (const_string "no")))
+ (set (attr "length")
+ (if_then_else
+ (and (ge (minus (match_dup 2) (pc)) (const_int 2))
+ (le (minus (match_dup 2) (pc)) (const_int 128))
+ (not (match_test "which_alternative")))
+ (const_int 2)
+ (if_then_else
+ (and (ge (minus (match_dup 2) (pc)) (const_int -250))
+ (le (minus (match_dup 2) (pc)) (const_int 256)))
+ (const_int 4)
+ (if_then_else
+ (and (ge (minus (match_dup 2) (pc)) (const_int -2040))
+ (le (minus (match_dup 2) (pc)) (const_int 2048)))
+ (const_int 6)
+ (const_int 8)))))
+ (set (attr "type")
+ (if_then_else
+ (eq_attr "length" "2")
+ (const_string "branch")
+ (const_string "multiple")))]
+)
+
(define_insn "cbranchsi4_insn"
[(set (pc) (if_then_else
(match_operator 0 "arm_comparison_operator"
Testing:
* Toolchain was built successfully with and without the ARMv8-M support
patches with the following multilib list:
armv6-m,armv7-m,armv7e-m,cortex-m7. The code generation for crtbegin.o,
crtend.o, crti.o, crtn.o, libgcc.a, libgcov.a, libc.a, libg.a,
libgloss-linux.a, libm.a, libnosys.a, librdimon.a, librdpmon.a, libstdc++.a
and libsupc++.a is unchanged for all these targets.
* GCC also showed no testsuite regression when targeting ARMv8-M Baseline
compared to ARMv6-M on ARM Fast Models and when targeting ARMv6-M and
ARMv7-M (compared to without the patch) * GCC was bootstrapped successfully
targeting Thumb-1 and targeting Thumb-2
Is this ok for stage3?
Best regards,
Thomas