Performance improvements.

git-svn-id: https://svn.code.sf.net/p/freertos/code/trunk@335 1d2547de-c912-0410-9cb9-b8ca96c0e9e2

diff --git a/Source/portable/MPLAB/PIC32MX/ISR_Support.h b/Source/portable/MPLAB/PIC32MX/ISR_Support.h
index 62d5ef1e197fef4b12494d1d5fd30c0e373d478e..208d7b80ee7aa53bdebe5c5e87d08922db1a6570 100644 (file)
--- a/Source/portable/MPLAB/PIC32MX/ISR_Support.h
+++ b/Source/portable/MPLAB/PIC32MX/ISR_Support.h
@@ -88,21 +88,25 @@
        ins             k1, k0, 10, 6\r
        ins                     k1, zero, 1, 4\r
 \r
-       /* Load, incrmement, then save the interrupt nesting count. */\r
+       /* s5 is used as the frame pointer. */\r
+       add                     s5, zero, sp\r
+\r
+       /* Check the nesting count value. */\r
        la                      k0, uxInterruptNesting\r
        lw                      s6, (k0)\r
-       addiu           s6, s6, 1\r
-       sw                      s6, 0(k0)\r
 \r
-       /* If it was zero, switch to the system stack.  If it was not zero then\r
-       we are already using the system stack.  s5 holds the old stack value -\r
-       this might be used to determine the cause of a general exception. */\r
-       add                     s5, zero, sp\r
-       addiu           s6, s6, -1\r
-       bne                     zero, s6, .+20\r
+       /* If the nesting count is 0 then swap to the the system stack, otherwise\r
+       the system stack is already being used. */\r
+       bne                     s6, zero, .+16\r
        nop\r
-       la                      s6, xISRStackTop\r
-       lw                      sp, (s6)\r
+\r
+       /* Swap to the system stack. */\r
+       la                      sp, xISRStackTop\r
+       lw                      sp, (sp)\r
+\r
+       /* Increment and save the nesting count. */\r
+       addiu           s6, s6, 1\r
+       sw                      s6, 0(k0)\r
 \r
        /* s6 holds the EPC value, we may want this during the context switch. */\r
        mfc0            s6, _CP0_EPC\r
@@ -132,7 +136,7 @@
        sw                      v0, 52(s5)\r
        sw                      s7, 48(s5)\r
        sw                      s6, portEPC_STACK_LOCATION(s5)\r
-       /* s5 has already been saved. */\r
+       /* s5 and s6 has already been saved. */\r
        sw                      s4,     36(s5)\r
        sw                      s3, 32(s5)\r
        sw                      s2, 28(s5)\r