Fix and improve coroutines for Darwin (macOS) ppc/ppc64. (#5975)

2 files changed, 72 insertions, 53 deletions

diff --git a/coroutine/ppc64/Context.S b/coroutine/ppc64/Context.S
index 1bd9268f93..f8561e0e7d 100644
--- a/coroutine/ppc64/Context.S
+++ b/coroutine/ppc64/Context.S
@@ -1,70 +1,89 @@
+; Based on the code by Samuel Williams. Created by Sergey Fedorov on 04/06/2022.
+; Credits to Samuel Williams, Rei Odaira and Iain Sandoe. Errors, if any, are mine.
+; Some relevant examples: https://github.com/gcc-mirror/gcc/blob/master/libphobos/libdruntime/config/powerpc/switchcontext.S
+; https://github.com/gcc-mirror/gcc/blob/master/libgcc/config/rs6000/darwin-gpsave.S
+; https://www.ibm.com/docs/en/aix/7.2?topic=epilogs-saving-gprs-only
+
+; Notice that this code is only for Darwin (macOS). Darwin ABI differs from AIX and ELF.
+; To add support for AIX, *BSD or *Linux, please make separate implementations.
+
 #define TOKEN_PASTE(x,y) x##y
 #define PREFIXED_SYMBOL(prefix,name) TOKEN_PASTE(prefix,name)
 
+.machine ppc64 ; = G5
 .text
-.align 3
 
 .globl PREFIXED_SYMBOL(SYMBOL_PREFIX,coroutine_transfer)
-PREFIXED_SYMBOL(SYMBOL_PREFIX,coroutine_transfer):
-	# Make space on the stack for caller registers
-	addi r1,r1,-152
+.align 2
 
-	# Save caller registers
-	std r14,0(r1)
-	std r15,8(r1)
-	std r16,16(r1)
-	std r17,24(r1)
-	std r18,32(r1)
-	std r19,40(r1)
-	std r20,48(r1)
-	std r21,56(r1)
-	std r22,64(r1)
-	std r23,72(r1)
-	std r24,80(r1)
-	std r25,88(r1)
-	std r26,96(r1)
-	std r27,104(r1)
-	std r28,112(r1)
-	std r29,120(r1)
-	std r30,128(r1)
-	std r31,136(r1)
+PREFIXED_SYMBOL(SYMBOL_PREFIX,coroutine_transfer):
+	; Make space on the stack for caller registers
+	; (Should we rather use red zone? See libphobos example.)
+	subi r1,r1,160
 
-	# Save return address
+	; Get LR
 	mflr r0
-	std r0,144(r1)
 
-	# Save stack pointer to first argument
+	; Save caller registers
+	std r31,0(r1)
+	std r30,8(r1)
+	std r29,16(r1)
+	std r28,24(r1)
+	std r27,32(r1)
+	std r26,40(r1)
+	std r25,48(r1)
+	std r24,56(r1)
+	std r23,64(r1)
+	std r22,72(r1)
+	std r21,80(r1)
+	std r20,88(r1)
+	std r19,96(r1)
+	std r18,104(r1)
+	std r17,112(r1)
+	std r16,120(r1)
+	std r15,128(r1)
+	std r14,136(r1)
+	std r13,144(r1)
+
+	; Save return address
+	; Possibly should rather be saved into linkage area, see libphobos and IBM docs
+	std r0,152(r1)
+
+	; Save stack pointer to first argument
 	std r1,0(r3)
 
-	# Load stack pointer from second argument
+	; Load stack pointer from second argument
 	ld r1,0(r4)
 
-	# Restore caller registers
-	ld r14,0(r1)
-	ld r15,8(r1)
-	ld r16,16(r1)
-	ld r17,24(r1)
-	ld r18,32(r1)
-	ld r19,40(r1)
-	ld r20,48(r1)
-	ld r21,56(r1)
-	ld r22,64(r1)
-	ld r23,72(r1)
-	ld r24,80(r1)
-	ld r25,88(r1)
-	ld r26,96(r1)
-	ld r27,104(r1)
-	ld r28,112(r1)
-	ld r29,120(r1)
-	ld r30,128(r1)
-	ld r31,136(r1)
+	; Load return address
+	ld r0,152(r1)
+
+	; Restore caller registers
+	ld r13,144(r1)
+	ld r14,136(r1)
+	ld r15,128(r1)
+	ld r16,120(r1)
+	ld r17,112(r1)
+	ld r18,104(r1)
+	ld r19,96(r1)
+	ld r20,88(r1)
+	ld r21,80(r1)
+	ld r22,72(r1)
+	ld r23,64(r1)
+	ld r24,56(r1)
+	ld r25,48(r1)
+	ld r26,40(r1)
+	ld r27,32(r1)
+	ld r28,24(r1)
+	ld r29,16(r1)
+	ld r30,8(r1)
+	ld r31,0(r1)
 
-	# Load return address
-	ld r0,144(r1)
+	; Set LR
 	mtlr r0
 
-	# Pop stack frame
-	addi r1,r1,152
+	; Pop stack frame
+	addi r1,r1,160
 
-	# Jump to return address
+	; Jump to return address
 	blr
diff --git a/coroutine/ppc64/Context.h b/coroutine/ppc64/Context.h
index 5b47511b9c..3e6f77f55a 100644
--- a/coroutine/ppc64/Context.h
+++ b/coroutine/ppc64/Context.h
@@ -12,7 +12,7 @@
 
 enum {
   COROUTINE_REGISTERS =
-  19  /* 18 general purpose registers (r14–r31) and 1 return address */
+  20  /* 19 general purpose registers (r13–r31) and 1 return address */
   + 4  /* space for fiber_entry() to store the link register */
 };
 
@@ -44,7 +44,7 @@ static inline void coroutine_initialize(
     memset(context->stack_pointer, 0, sizeof(void*) * COROUTINE_REGISTERS);
 
     /* Skip a global prologue that sets the TOC register */
-    context->stack_pointer[18] = ((char*)start) + 8;
+    context->stack_pointer[19] = ((char*)start) + 8;
 }
 
 struct coroutine_context * coroutine_transfer(struct coroutine_context * current, struct coroutine_context * target);