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[committed] MMIX: Handle LRA FP-to-SP-elimination oddity

Message ID alpine.BSF.2.20.16.2308132213580.11350@arjuna.pair.com
State New
Headers show
Series [committed] MMIX: Handle LRA FP-to-SP-elimination oddity | expand

Commit Message

Hans-Peter Nilsson Aug. 14, 2023, 2:16 a.m. UTC 
When LRA is in progress, it can try and validate insns
half-way through frame-pointer (FP) to stack-pointer (SP)
elimination.  Operands have then been substituted where the
offset is from the SP elimination but the register is the
(hard) frame-pointer:

lra-eliminations.cc:lra_eliminate_regs_1:370:
 rtx to = subst_p ? ep->to_rtx : ep->from_rtx;

In this regard reload played nicely.  Unfortunately, the
frame_pointer_operand predicate in mmix/predicates.md barfs
on such an address.  This broke the use of the MMIX
frame_pointer_operand predicate (and the Yf constraint),
used only in the nonlocal_goto_receiver expansion (which is
used in e.g. code generated for C++ "catch").

Force MMIX frame_pointer_operand to accept an FP+offset for
the duration of lra_in_progress.

	* config/mmix/predicates.md (frame_pointer_operand): Handle FP+offset
	when lra_in_progress.
---
 gcc/config/mmix/predicates.md | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)
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Patch

diff --git a/gcc/config/mmix/predicates.md b/gcc/config/mmix/predicates.md
index 4a9b0177a786..64e77fa92d00 100644
--- a/gcc/config/mmix/predicates.md
+++ b/gcc/config/mmix/predicates.md
@@ -171,4 +171,14 @@  (define_predicate "frame_pointer_operand"
     (match_code "plus")
     (match_code "reg" "0")
     (match_code "const_int" "1")
-    (match_test "XEXP (op, 0) == stack_pointer_rtx"))))
+    (ior
+     (match_test "XEXP (op, 0) == stack_pointer_rtx")
+     ;; We can temporarily have a FP+offset here, where we (for FP)
+     ;; accept only FP and the equivalent elimination of SP+offset.
+     ;; See lra_eliminate_regs_1 in lra-eliminations.cc c:a line 370:
+     ;;  "rtx to = subst_p ? ep->to_rtx : ep->from_rtx;"
+     (and
+      (match_test "lra_in_progress")
+      (ior
+       (match_test "XEXP (op, 0) == hard_frame_pointer_rtx")
+       (match_test "XEXP (op, 0) == frame_pointer_rtx")))))))