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* [gcc r11-9879] Darwin, rs6000: Amend lo_sum use for forced constants [PR104117].
@ 2022-04-14 5:28 Iain D Sandoe
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From: Iain D Sandoe @ 2022-04-14 5:28 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:53254184bda6305ac38e6e37480303b9f167b5ae
commit r11-9879-g53254184bda6305ac38e6e37480303b9f167b5ae
Author: Iain Sandoe <iain@sandoe.co.uk>
Date: Mon Feb 7 15:36:35 2022 +0000
Darwin, rs6000: Amend lo_sum use for forced constants [PR104117].
Two issues resulted in this PR, which manifests when we force a constant into
memory in LRA (in PIC code on Darwin). The presence of such forced constants
is quite dependent on other RTL optimisations, and it is easy for the issue to
become latent for a specific case.
First, in the Darwin-specific rs6000 backend code, we were not being careful
enough in rejecting invalid symbolic addresses. Specifically, when generating
PIC code, we require a SYMBOL_REF to be wrapped in an UNSPEC_MACHOPIC_OFFSET.
We now split the Darwin high/low selectors into two:
1. One that handles non-PIC addresses (kernel mode, mdynamic-no-pic).
2. One that handles PIC addresses and rejects SYMBOL_REFs unless they are
suitably wrapped in the MACHOPIC_OFFSET unspec.
The second case is handled by providing a new predicate (macho_pic_address)
that checks the requirements.
Backported from 4c3792d448964f7bd99e7eac2c29c9eb7c2bfb84 and
f1b3e3853329b58fb2e50c17487df2ecbc4a5608
Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
Co-authored-by: Vladimir Makarov <vmakarov@redhat.com>
PR target/104117
gcc/ChangeLog:
* config/rs6000/rs6000.c (darwin_rs6000_legitimate_lo_sum_const_p):
Check for UNSPEC_MACHOPIC_OFFSET wrappers on symbolic addresses when
emitting PIC code.
(legitimate_lo_sum_address_p): Likewise.
(rs6000_legitimize_address): Do not apply the TLS processing to
Darwin.
* config/rs6000/darwin.md (@machopic_high_<mode>): New.
(@machopic_low_<mode>): New.
* config/rs6000/predicates.md (macho_pic_address): New.
Diff:
---
gcc/config/rs6000/darwin.md | 19 +++++++++++++++----
gcc/config/rs6000/predicates.md | 14 ++++++++++++++
gcc/config/rs6000/rs6000.c | 40 +++++++++++++++++++++++++++++++++++++---
3 files changed, 66 insertions(+), 7 deletions(-)
diff --git a/gcc/config/rs6000/darwin.md b/gcc/config/rs6000/darwin.md
index 937534286bf..66408b61426 100644
--- a/gcc/config/rs6000/darwin.md
+++ b/gcc/config/rs6000/darwin.md
@@ -121,21 +121,32 @@ You should have received a copy of the GNU General Public License
stw %0,lo16(%2)(%1)"
[(set_attr "type" "store")])
-;; 64-bit MachO load/store support
-
;; Mach-O PIC.
(define_insn "@macho_high_<mode>"
[(set (match_operand:P 0 "gpc_reg_operand" "=b*r")
(high:P (match_operand 1 "" "")))]
- "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN)"
+ "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN) && !flag_pic"
"lis %0,ha16(%1)")
(define_insn "@macho_low_<mode>"
[(set (match_operand:P 0 "gpc_reg_operand" "=r")
(lo_sum:P (match_operand:P 1 "gpc_reg_operand" "b")
(match_operand 2 "" "")))]
- "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN)"
+ "TARGET_MACHO && (DEFAULT_ABI == ABI_DARWIN) && !flag_pic"
+ "la %0,lo16(%2)(%1)")
+
+(define_insn "@machopic_high_<mode>"
+ [(set (match_operand:P 0 "gpc_reg_operand" "=b*r")
+ (high:P (match_operand 1 "macho_pic_address" "")))]
+ "TARGET_MACHO && flag_pic"
+ "lis %0,ha16(%1)")
+
+(define_insn "@machopic_low_<mode>"
+ [(set (match_operand:P 0 "gpc_reg_operand" "=r")
+ (lo_sum:P (match_operand:P 1 "gpc_reg_operand" "b")
+ (match_operand 2 "macho_pic_address" "")))]
+ "TARGET_MACHO && flag_pic"
"la %0,lo16(%2)(%1)")
(define_split
diff --git a/gcc/config/rs6000/predicates.md b/gcc/config/rs6000/predicates.md
index 55dc357b84c..f03560b9c06 100644
--- a/gcc/config/rs6000/predicates.md
+++ b/gcc/config/rs6000/predicates.md
@@ -1952,3 +1952,17 @@
(if_then_else (match_test "TARGET_VSX")
(match_operand 0 "reg_or_cint_operand")
(match_operand 0 "const_int_operand")))
+
+;; Return true if the operand is a valid Mach-O pic address.
+;;
+(define_predicate "macho_pic_address"
+ (match_code "const,unspec")
+{
+ if (GET_CODE (op) == CONST)
+ op = XEXP (op, 0);
+
+ if (GET_CODE (op) == UNSPEC && XINT (op, 1) == UNSPEC_MACHOPIC_OFFSET)
+ return CONSTANT_P (XVECEXP (op, 0, 0));
+ else
+ return false;
+})
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 608f30146e7..0421dc7adb3 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -8237,8 +8237,14 @@ darwin_rs6000_legitimate_lo_sum_const_p (rtx x, machine_mode mode)
if (GET_CODE (x) == CONST)
x = XEXP (x, 0);
+ /* If we are building PIC code, then any symbol must be wrapped in an
+ UNSPEC_MACHOPIC_OFFSET so that it will get the picbase subtracted. */
+ bool machopic_offs_p = false;
if (GET_CODE (x) == UNSPEC && XINT (x, 1) == UNSPEC_MACHOPIC_OFFSET)
- x = XVECEXP (x, 0, 0);
+ {
+ x = XVECEXP (x, 0, 0);
+ machopic_offs_p = true;
+ }
rtx sym = NULL_RTX;
unsigned HOST_WIDE_INT offset = 0;
@@ -8269,6 +8275,9 @@ darwin_rs6000_legitimate_lo_sum_const_p (rtx x, machine_mode mode)
if (sym)
{
tree decl = SYMBOL_REF_DECL (sym);
+ /* As noted above, PIC code cannot use a bare SYMBOL_REF. */
+ if (TARGET_MACHO && flag_pic && !machopic_offs_p)
+ return false;
#if TARGET_MACHO
if (MACHO_SYMBOL_INDIRECTION_P (sym))
/* The decl in an indirection symbol is the original one, which might
@@ -8856,7 +8865,7 @@ legitimate_lo_sum_address_p (machine_mode mode, rtx x, int strict)
return false;
x = XEXP (x, 1);
- if (TARGET_ELF || TARGET_MACHO)
+ if (TARGET_ELF)
{
bool large_toc_ok;
@@ -8882,7 +8891,32 @@ legitimate_lo_sum_address_p (machine_mode mode, rtx x, int strict)
return CONSTANT_P (x) || large_toc_ok;
}
+ else if (TARGET_MACHO)
+ {
+ if (GET_MODE_NUNITS (mode) != 1)
+ return false;
+ if (GET_MODE_SIZE (mode) > UNITS_PER_WORD
+ && !(/* see above */
+ TARGET_HARD_FLOAT && (mode == DFmode || mode == DDmode)))
+ return false;
+#if TARGET_MACHO
+ if (MACHO_DYNAMIC_NO_PIC_P || !flag_pic)
+ return CONSTANT_P (x);
+#endif
+ /* Macho-O PIC code from here. */
+ if (GET_CODE (x) == CONST)
+ x = XEXP (x, 0);
+
+ /* SYMBOL_REFs need to be wrapped in an UNSPEC_MACHOPIC_OFFSET. */
+ if (SYMBOL_REF_P (x))
+ return false;
+ /* So this is OK if the wrapped object is const. */
+ if (GET_CODE (x) == UNSPEC
+ && XINT (x, 1) == UNSPEC_MACHOPIC_OFFSET)
+ return CONSTANT_P (XVECEXP (x, 0, 0));
+ return CONSTANT_P (x);
+ }
return false;
}
@@ -8936,7 +8970,7 @@ rs6000_legitimize_address (rtx x, rtx oldx ATTRIBUTE_UNUSED,
else
return force_reg (Pmode, x);
}
- if (SYMBOL_REF_P (x))
+ if (SYMBOL_REF_P (x) && !TARGET_MACHO)
{
enum tls_model model = SYMBOL_REF_TLS_MODEL (x);
if (model != 0)
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