Reveal nodes on demand rather than up-front

Replaces #2055
Closes #2055
Fixes #2050

Author: JasonGross

fiat-amd64/fiat_curve25519_sub/clang_19_1_0_O0.asm

@@ -0,0 +1,54 @@
+        .globl  _Z14fiat_25519_subPmPKmS1_
+_Z14fiat_25519_subPmPKmS1_:
+        push    rbp
+        mov     rbp, rsp
+        mov     qword ptr [rbp - 8], rdi
+        mov     qword ptr [rbp - 16], rsi
+        mov     qword ptr [rbp - 24], rdx
+        mov     rcx, qword ptr [rbp - 16]
+        movabs  rax, 4503599627370458
+        add     rax, qword ptr [rcx]
+        mov     rcx, qword ptr [rbp - 24]
+        sub     rax, qword ptr [rcx]
+        mov     qword ptr [rbp - 32], rax
+        mov     rcx, qword ptr [rbp - 16]
+        movabs  rax, 4503599627370494
+        add     rax, qword ptr [rcx + 8]
+        mov     rcx, qword ptr [rbp - 24]
+        sub     rax, qword ptr [rcx + 8]
+        mov     qword ptr [rbp - 40], rax
+        mov     rcx, qword ptr [rbp - 16]
+        movabs  rax, 4503599627370494
+        add     rax, qword ptr [rcx + 16]
+        mov     rcx, qword ptr [rbp - 24]
+        sub     rax, qword ptr [rcx + 16]
+        mov     qword ptr [rbp - 48], rax
+        mov     rcx, qword ptr [rbp - 16]
+        movabs  rax, 4503599627370494
+        add     rax, qword ptr [rcx + 24]
+        mov     rcx, qword ptr [rbp - 24]
+        sub     rax, qword ptr [rcx + 24]
+        mov     qword ptr [rbp - 56], rax
+        mov     rcx, qword ptr [rbp - 16]
+        movabs  rax, 4503599627370494
+        add     rax, qword ptr [rcx + 32]
+        mov     rcx, qword ptr [rbp - 24]
+        sub     rax, qword ptr [rcx + 32]
+        mov     qword ptr [rbp - 64], rax
+        mov     rcx, qword ptr [rbp - 32]
+        mov     rax, qword ptr [rbp - 8]
+        mov     qword ptr [rax], rcx
+        mov     rcx, qword ptr [rbp - 40]
+        mov     rax, qword ptr [rbp - 8]
+        mov     qword ptr [rax + 8], rcx
+        mov     rcx, qword ptr [rbp - 48]
+        mov     rax, qword ptr [rbp - 8]
+        mov     qword ptr [rax + 16], rcx
+        mov     rcx, qword ptr [rbp - 56]
+        mov     rax, qword ptr [rbp - 8]
+        mov     qword ptr [rax + 24], rcx
+        mov     rcx, qword ptr [rbp - 64]
+        mov     rax, qword ptr [rbp - 8]
+        mov     qword ptr [rax + 32], rcx
+        pop     rbp
+        ret

fiat-amd64/fiat_curve25519_sub/gcc_14_1_0.asm

@@ -0,0 +1,77 @@
+        .globl  _Z14fiat_25519_subPmPKmS1_
+_Z14fiat_25519_subPmPKmS1_:
+        push    rbp
+        mov     rbp, rsp
+        mov     QWORD PTR [rbp-56], rdi
+        mov     QWORD PTR [rbp-64], rsi
+        mov     QWORD PTR [rbp-72], rdx
+        mov     rax, QWORD PTR [rbp-64]
+        mov     rdx, QWORD PTR [rax]
+        mov     rax, QWORD PTR [rbp-72]
+        mov     rax, QWORD PTR [rax]
+        sub     rdx, rax
+        movabs  rax, 4503599627370458
+        add     rax, rdx
+        mov     QWORD PTR [rbp-8], rax
+        mov     rax, QWORD PTR [rbp-64]
+        add     rax, 8
+        mov     rdx, QWORD PTR [rax]
+        mov     rax, QWORD PTR [rbp-72]
+        add     rax, 8
+        mov     rax, QWORD PTR [rax]
+        sub     rdx, rax
+        movabs  rax, 4503599627370494
+        add     rax, rdx
+        mov     QWORD PTR [rbp-16], rax
+        mov     rax, QWORD PTR [rbp-64]
+        add     rax, 16
+        mov     rdx, QWORD PTR [rax]
+        mov     rax, QWORD PTR [rbp-72]
+        add     rax, 16
+        mov     rax, QWORD PTR [rax]
+        sub     rdx, rax
+        movabs  rax, 4503599627370494
+        add     rax, rdx
+        mov     QWORD PTR [rbp-24], rax
+        mov     rax, QWORD PTR [rbp-64]
+        add     rax, 24
+        mov     rdx, QWORD PTR [rax]
+        mov     rax, QWORD PTR [rbp-72]
+        add     rax, 24
+        mov     rax, QWORD PTR [rax]
+        sub     rdx, rax
+        movabs  rax, 4503599627370494
+        add     rax, rdx
+        mov     QWORD PTR [rbp-32], rax
+        mov     rax, QWORD PTR [rbp-64]
+        add     rax, 32
+        mov     rdx, QWORD PTR [rax]
+        mov     rax, QWORD PTR [rbp-72]
+        add     rax, 32
+        mov     rax, QWORD PTR [rax]
+        sub     rdx, rax
+        movabs  rax, 4503599627370494
+        add     rax, rdx
+        mov     QWORD PTR [rbp-40], rax
+        mov     rax, QWORD PTR [rbp-56]
+        mov     rdx, QWORD PTR [rbp-8]
+        mov     QWORD PTR [rax], rdx
+        mov     rax, QWORD PTR [rbp-56]
+        lea     rdx, [rax+8]
+        mov     rax, QWORD PTR [rbp-16]
+        mov     QWORD PTR [rdx], rax
+        mov     rax, QWORD PTR [rbp-56]
+        lea     rdx, [rax+16]
+        mov     rax, QWORD PTR [rbp-24]
+        mov     QWORD PTR [rdx], rax
+        mov     rax, QWORD PTR [rbp-56]
+        lea     rdx, [rax+24]
+        mov     rax, QWORD PTR [rbp-32]
+        mov     QWORD PTR [rdx], rax
+        mov     rax, QWORD PTR [rbp-56]
+        lea     rdx, [rax+32]
+        mov     rax, QWORD PTR [rbp-40]
+        mov     QWORD PTR [rdx], rax
+        nop
+        pop     rbp
+        ret