From: Taylor R Campbell <campbell@mumble.net>
Date: Wed, 2 Jan 2019 06:10:52 +0000 (+0000)
Subject: Load the fallback into rax so caller needs no conditional branch.
X-Git-Tag: mit-scheme-pucked-10.1.20~11^2~80^2~13
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=8d274971d679e40e298356daad01cff96b59384a;p=mit-scheme.git

Load the fallback into rax so caller needs no conditional branch.

WARNING: This changes the amd64 compiled code interface so that new
compiled code requires a new microcode.  (However, a new microcode
should handle old compiled code without trouble, since old compiled
code treats rax as garbage at this point, and LEA does not affect
flags.)
---

diff --git a/src/compiler/machines/x86-64/rules3.scm b/src/compiler/machines/x86-64/rules3.scm
index 787efe41c..3193f00e6 100644
--- a/src/compiler/machines/x86-64/rules3.scm
+++ b/src/compiler/machines/x86-64/rules3.scm
@@ -110,10 +110,7 @@ USA.
 	     (else
 	      (LAP (MOV Q (R ,rdx) (&U ,frame-size))
 		   ,@(invoke-hook/subroutine entry:compiler-apply-setup))))
-	 (JNE (@PCR ,generic))
-	 (JMP (R ,rax))
-	(LABEL ,generic)
-	 ,@(invoke-hook entry:compiler-shortcircuit-apply))))
+	 (JMP (R ,rax)))))
 
 (define-rule statement
   (INVOCATION:JUMP (? frame-size) (? continuation) (? label))
diff --git a/src/microcode/cmpauxmd/x86-64.m4 b/src/microcode/cmpauxmd/x86-64.m4
index f98d8426c..38dbabaf6 100644
--- a/src/microcode/cmpauxmd/x86-64.m4
+++ b/src/microcode/cmpauxmd/x86-64.m4
@@ -613,6 +613,9 @@ define_hook_label(apply_setup)
 	ret
 
 asm_apply_setup_fail:
+	# Load the fallback address into rax, where compiled code will
+	# jump.
+	OP(lea,q)	TW(ABS(EVR(asm_sc_apply_generic)),REG(rax))
 	ret
 
 define(define_apply_setup_fixed_size,
@@ -631,6 +634,7 @@ define_hook_label(apply_setup_size_$1)
 	ret
 
 asm_apply_setup_size_$1_fail:
+	OP(lea,q)	TW(ABS(EVR(asm_sc_apply_generic)),REG(rax))
 	OP(mov,q)	TW(IMM(HEX($1)),REG(rdx))
 	ret')