From: Mark Wooding <mdw@distorted.org.uk>
Date: Thu, 7 Nov 2019 01:46:50 +0000 (+0000)
Subject: math/mpx-mul4-*-sse2.S (mpxmont_redc4): Fix end-of-outer-loop commentary.
X-Git-Tag: 2.6.0~15
X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/commitdiff_plain/6966e7a60a87415d3d02230608a98016c03a7a51

math/mpx-mul4-*-sse2.S (mpxmont_redc4): Fix end-of-outer-loop commentary.

  * The carry loop is wrong if the destination is an exact multiple of
    four limbs.  Fortunately, it isn't.

  * The initial pass feeds into the main loop unconditionally, unlike
    `mpxmont_mul4_...' (from which I think the commentary was
    uncritically copied), so being at the end of it doesn't tell you
    anything about whether to start another.  And, indeed, we do indeed
    check the loop-end condition.
---

diff --git a/math/mpx-mul4-amd64-sse2.S b/math/mpx-mul4-amd64-sse2.S
index a37aba69..17c4f1ad 100644
--- a/math/mpx-mul4-amd64-sse2.S
+++ b/math/mpx-mul4-amd64-sse2.S
@@ -1260,7 +1260,9 @@ FUNC(mpxmont_redc4_amd64_sse2)
 	cmp	rdi, DVL4
 	jb	0b
 
-	// Deal with the tail end.
+	// Deal with the tail end.  Note that the actual destination length
+	// won't be an exacty number of blocks of four, so it's safe to just
+	// drop through here.
 7:	add	[rdi], C
 	mov	C, 0
 	add	rdi, 4
@@ -1268,9 +1270,7 @@ FUNC(mpxmont_redc4_amd64_sse2)
 	cmp	rdi, DVL
 	jb	7b
 
-	// All done for this iteration.  Start the next.  (This must have at
-	// least one follow-on iteration, or we'd not have started this outer
-	// loop.)
+	// All done for this iteration.  Start the next.
 8:	mov	rdi, DV			// -> Z = dv[i]
 	mov	rbx, NV			// -> X = nv[0]
 	cmp	rdi, DVLO		// all done yet?
diff --git a/math/mpx-mul4-x86-sse2.S b/math/mpx-mul4-x86-sse2.S
index 9e1d4782..7e7173fc 100644
--- a/math/mpx-mul4-x86-sse2.S
+++ b/math/mpx-mul4-x86-sse2.S
@@ -1062,7 +1062,9 @@ FUNC(mpxmont_redc4_x86_sse2)
 	cmp	edi, esi
 	jb	0b
 
-	// Deal with the tail end.
+	// Deal with the tail end.  Note that the actual destination length
+	// won't be an exact number of blocks of four, so it's safe to just
+	// drop through here.
 7:	add	[edi], eax
 	mov	eax, 0
 	add	edi, 4
@@ -1070,9 +1072,7 @@ FUNC(mpxmont_redc4_x86_sse2)
 	cmp	edi, edx
 	jb	7b
 
-	// All done for this iteration.  Start the next.  (This must have at
-	// least one follow-on iteration, or we'd not have started this outer
-	// loop.)
+	// All done for this iteration.  Start the next.
 8:	mov	edi, [SP + 0]		// -> dv[i - 1]
 	mov	ebx, [BP + 28]		// -> X = nv[0]
 	lea	edx, [SP + 44]		// -> space for Y