[GitHub] [incubator-nuttx] xiaoxiang781216 commented on a diff in pull request #7099: armv7-a/r: modify regs index to improve exception performance

[GitBox <gi...@apache.org>]

xiaoxiang781216 commented on code in PR #7099:
URL: https://github.com/apache/incubator-nuttx/pull/7099#discussion_r972257539


##########
arch/arm/src/armv7-a/arm_vectors.S:
##########
@@ -768,13 +710,14 @@ arm_vectorfiq:
 
 	/* Life is simple when everything is FIQ mode */
 
-	mov		r14, r0				/* (FIQ) r14=Register storage area */
+	ldmia		r0, {r13, r14}^			/* Restore user mode r13 and r14 */
+	add		r14, r0, #8
 	ldmia		r14!, {r0-r7}			/* Restore common r0-r7 */
-	ldmia		r14, {r8-r14}^			/* Restore user mode r8-r14 */
+	ldmia		r14, {r8-r12}^			/* Restore user mode r8-r12 */

Review Comment:
   ```suggestion
   	ldmia		r14!, {r8-r12}^			/* Restore user mode r8-r12 */
   ```
   and remove line 717



##########
arch/arm/src/armv7-a/arm_vectors.S:
##########
@@ -698,62 +652,50 @@ arm_vectorfiq:
 	/* Save the LR and SPSR onto the SYS mode stack before switch. */
 
 	sub		lr, lr, #4
-	srsdb		sp, #PSR_MODE_SYS
+	srsdb		sp!, #PSR_MODE_SYS
 
 	cpsid		if, #PSR_MODE_SYS		/* Switch to SYS mode */
 
 	/* Create a context structure.  First set aside a stack frame
 	 * and store r0-r12 into the frame.
 	 */
 
-	sub		sp, sp, #XCPTCONTEXT_SIZE
-	stmia		sp, {r0-r12}			/* Save the SYS mode regs */
+	stmdb		sp!, {r0-r12}			/* Save the SYS mode regs */
 
-	/* Get the correct values of USR/SYS r13(sp) and r14(lr) in r1 and r2 */
-
-	add		r1, sp, #XCPTCONTEXT_SIZE
-	mov		r2, r14
-
-	/* Save r13(sp), r14(lr) */
+	/* Get the correct values of USR/SYS r13(sp) in r1 and
+	 * save r13 and r14 into the frame.
+	 */
 
-	add		r0, sp, #(4*REG_SP)		/* Offset to pc, cpsr storage */
-	stmia		r0, {r1-r2}
+	add		r1, sp, #(XCPTCONTEXT_SIZE-4*REG_R0)
+	stmdb		sp!, {r1, r14}
 
 #ifdef CONFIG_ARCH_FPU
 	/* Save the state of the floating point registers. */
 
-	add		r0, sp, #(4*REG_S0)		/* R1=Address of FP register storage */
-	savefpu		r0, r1
+	savefpu		sp, r1
 #endif
 
 	/* Then call the FIQ handler with interrupts disabled. */
 
 	mov		fp, #0				/* Init frame pointer */
 	mov		r0, sp				/* Get r0=xcp */
 
+	mov		r4, sp				/* Save the SP in a preserved register */
+
 #if CONFIG_ARCH_INTERRUPTSTACK > 7
 	/* Call arm_decodefiq() on the interrupt stack */
 
 	setfiqstack	r1, r4				/* SP = interrupt stack top */

Review Comment:
   ```suggestion
   	setfiqstack	r1, r3				/* SP = interrupt stack top */
   ```



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