Fix destroyed_at_c_call on RISC-V (ocaml#10349)

* caml_c_call clobbers s2 * Changes (cherry picked from commit 93a9b2d)
edwintorok · Jun 26, 2021 · 2c90e8f · 2c90e8f
1 parent b92ecd3
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diff --git a/Changes b/Changes
@@ -7,6 +7,9 @@ OCaml 4.12, maintenance version
   platforms without AFL support.
   (David Allsopp, review by Xavier Leroy)
 
+- #10349: Fix destroyed_at_c_call on RISC-V
+  (Mark Shinwell, review by Nicolás Ojeda Bär)
+
 - #10294, #10295: fix an assert-failure in pattern-matching compilation
   (Gabriel Scherer, review by Thomas Refis and Luc Maranget,
    report by Nicolás Ojeda Bär)

diff --git a/asmcomp/riscv/proc.ml b/asmcomp/riscv/proc.ml
@@ -233,9 +233,10 @@ let regs_are_volatile _ = false
 (* Registers destroyed by operations *)
 
 let destroyed_at_c_call =
-  (* s0-s11 and fs0-fs11 are callee-save *)
+  (* s0-s11 and fs0-fs11 are callee-save.  However s2 needs to be in this
+     list since it is clobbered by caml_c_call itself. *)
   Array.of_list(List.map phys_reg
-    [0; 1; 2; 3; 4; 5; 6; 7; 16; 17; 18; 19; 20; 22;
+    [0; 1; 2; 3; 4; 5; 6; 7; 8; 16; 17; 18; 19; 20; 22;
      100; 101; 102; 103; 104; 105; 106; 107; 110; 111; 112; 113; 114; 115; 116;
      117; 128; 129; 130; 131])