From: Taylor R Campbell <campbell@mumble.net>
Date: Fri, 4 Jan 2019 04:58:51 +0000 (+0000)
Subject: Use ret for returns from interface and from generic arithmetic hooks.
X-Git-Tag: mit-scheme-pucked-10.1.20~11^2~80^2~8
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=31163e25df96787629821c16ce3548b7bd6f0047;p=mit-scheme.git

Use ret for returns from interface and from generic arithmetic hooks.

Let's take advantage of the return address stack branch target
predictor rather than unceremoniously trash it, shall we?
---

diff --git a/src/microcode/cmpauxmd/x86-64.m4 b/src/microcode/cmpauxmd/x86-64.m4
index 336b98291..2a241d511 100644
--- a/src/microcode/cmpauxmd/x86-64.m4
+++ b/src/microcode/cmpauxmd/x86-64.m4
@@ -507,8 +507,8 @@ define_debugging_label(scheme_to_interface_return)
 
 define_c_label(interface_to_scheme)
 	# rax = interface_to_scheme
-	# rcx = compiled entry address, needed by compiled code; 0 if return
-	# rdx = compiled PC
+	# rcx = compiled entry/return address, needed by compiled code
+	# rdx = compiled PC, or interface_to_scheme_return
 ifdef(`WIN32',						# Register block = %rsi
 `	OP(mov,q)	TW(ABS(EVR(RegistersPtr)),regs)',
 `	OP(lea,q)	TW(ABS(EVR(Registers)),regs)')
@@ -525,7 +525,12 @@ ifdef(`WIN32',						# Register block = %rsi
 	OP(mov,q)	TW(REG(rax),REG(r8))		# Preserve if used
 	OP(and,q)	TW(rmask,REG(r8))		# Restore potential dynamic link
 	OP(mov,q)	TW(REG(r8),QOF(REGBLOCK_DLINK(),regs))
-	jmp	IJMP(REG(rdx))			# Invoke
+	jmp	IJMP(REG(rdx))			# Invoke entry or handler
+
+define_c_label(interface_to_scheme_return)
+	# rcx = compiled return address
+	OP(push,q)	REG(rcx)
+	ret					# Invoke return
 
 IF_WIN32(`
 use_external_code(EFR(WinntExceptionTransferHook))
@@ -770,9 +775,8 @@ define_debugging_label(set_interrupt_enables_no_stackoverflow)
 
 declare_alignment(2)
 asm_generic_return_rax:
-	OP(pop,q)	REG(rcx)
-	OP(and,q)	TW(rmask,REG(rcx))
-	jmp	IJMP(REG(rcx))			# Invoke return
+	OP(and,q)	TW(rmask,IND(REG(rsp)))
+	ret					# Invoke return
 
 declare_alignment(2)
 asm_generic_fixnum_result:
diff --git a/src/microcode/cmpint.c b/src/microcode/cmpint.c
index 78f69c739..3e5ef1995 100644
--- a/src/microcode/cmpint.c
+++ b/src/microcode/cmpint.c
@@ -210,6 +210,7 @@ static long make_apply_trampoline
 
 extern c_func_t ASM_ENTRY_POINT (interface_to_C);
 extern c_func_t ASM_ENTRY_POINT (interface_to_scheme);
+extern c_func_t ASM_ENTRY_POINT (interface_to_scheme_return);
 
 #define ENTER_SCHEME_ENTRY(ep) do					\
 {									\
diff --git a/src/microcode/cmpintmd/x86-64.h b/src/microcode/cmpintmd/x86-64.h
index 1c89e6caf..78fa05be0 100644
--- a/src/microcode/cmpintmd/x86-64.h
+++ b/src/microcode/cmpintmd/x86-64.h
@@ -165,8 +165,8 @@ typedef uint8_t insn_t;
 #define CC_ENTRY_ADDRESS_PTR(e)		(e)
 #define CC_ENTRY_ADDRESS_PC(e)		((e) + (((const int64_t *) (e))[-1]))
 
-#define CC_RETURN_ADDRESS_PTR(r)	0
-#define CC_RETURN_ADDRESS_PC(r)		(r)
+#define CC_RETURN_ADDRESS_PTR(r)	(r)
+#define CC_RETURN_ADDRESS_PC(r)		((insn_t *) interface_to_scheme_return)
 
 insn_t * cc_return_address_to_entry_address (insn_t *);