ARC: entry.S: micro-optimize Trap handler (62fb6403) · Commits · 戴 / test

Elide the need to re-read ECR in Trap handler by ensuring that EXCEPTION_PROLOGUE does that at the very end just before returning to Trap handler ARCv2 EXCEPTION_PROLOGUE already did that, so same for ARcompact and the common trap handler adjusted to use cached ECR Signed-off-by:

Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/entry-compact.h

+3 −2

Original line number	Diff line number	Diff line
		@@ -181,8 +181,6 @@
		/* ARC700 doesn't provide auto-stack switching */
		SWITCH_TO_KERNEL_STK

		lr r9, [ecr]
		st r9, [sp, 8] /* ECR */
		st r0, [sp, 4] /* orig_r0, needed only for sys calls */

		/* Restore r9 used to code the early prologue */
		@@ -198,6 +196,9 @@
		PUSHAX lp_end
		PUSHAX lp_start
		PUSHAX erbta

		lr r9, [ecr]
		st r9, [sp, PT_event] /* EV_Trap expects r9 to have ECR */
		.endm

		/*--------------------------------------------------------------

arch/arc/kernel/entry.S

+2 −2

Original line number	Diff line number	Diff line
		@@ -258,8 +258,8 @@ ENTRY(EV_Trap)
		EXCEPTION_PROLOGUE

		;============ TRAP 1 :breakpoints
		lr r10, [ecr]
		bmsk.f 0, r10, 7
		; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR)
		bmsk.f 0, r9, 7
		bnz trap_with_param

		;============ TRAP (no param): syscall top level

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