From 204303c81e82ddd01e7dc5a5a63719d476f9043c Mon Sep 17 00:00:00 2001 From: Jeff Law Date: Tue, 9 May 2023 07:18:45 -0600 Subject: Eliminate more comparisons on the H8 port This patch fixes a minor code quality issue I found while testing LRA on the H8. Specifically we have a peephole which converts a comparison of a memory location against zero into a load + comparison which is actually more efficient. This triggers when there are registers available at the right point during peephole2. If the load is not a mode dependent address we can actually do better by realizing the load itself sets the proper flags and eliminate the comparison. I may have expected this to happen when I wrote the original peephole2, but cmpelim runs before peephole2, so clearly if we want to eliminate the comparison we have to do it manually. gcc/ * config/h8300/testcompare.md: Add peephole2 which uses a memory load to set flags, thus eliminating a compare against zero. --- gcc/config/h8300/testcompare.md | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'gcc') diff --git a/gcc/config/h8300/testcompare.md b/gcc/config/h8300/testcompare.md index 81dce1d..efa66d2 100644 --- a/gcc/config/h8300/testcompare.md +++ b/gcc/config/h8300/testcompare.md @@ -171,13 +171,25 @@ (set_attr "length_table" "*,add")]) ;; Convert a memory comparison to a move if there is a scratch register. +;; This is preferred over the next as we can proactively avoid the +;; comparison. +(define_peephole2 + [(match_scratch:QHSI 1 "r") + (set (reg:CC CC_REG) + (compare (match_operand:QHSI 0 "memory_operand" "") + (const_int 0)))] + "!mode_dependent_address_p (XEXP (operands[0], 0), MEM_ADDR_SPACE (operands[0]))" + [(parallel [(set (reg:CCZN CC_REG) (compare:CCZN (match_dup 0) (const_int 0))) + (set (match_dup 1) (match_dup 0))])]) +;; Similarly, but used when the memory reference is an autoinc address +;; mode. (define_peephole2 [(match_scratch:QHSI 1 "r") (set (reg:CC CC_REG) (compare (match_operand:QHSI 0 "memory_operand" "") (const_int 0)))] - "" + "mode_dependent_address_p (XEXP (operands[0], 0), MEM_ADDR_SPACE (operands[0]))" [(parallel [(set (match_dup 1) (match_dup 0)) (clobber (reg:CC CC_REG))]) (set (reg:CC CC_REG) (compare:CC (match_dup 1) (const_int 0)))]) -- cgit v1.1