[Guile-commits] 01/03: Spill whole words to stack, even for uint8_t args

[Andy Wingo]

wingo pushed a commit to branch master
in repository guile.

commit 2784bee8e52813227a19ecbdc62f2f3eecbe6974
Author: Andy Wingo <wingo@igalia.com>
AuthorDate: Thu Jul 30 14:26:37 2020 +0200

    Spill whole words to stack, even for uint8_t args
    
    * lightening/lightening.c (abi_gpr_to_mem): Write whole words when
      spilling GPRs to the stack.  Always correct given that all Lightening
      operations that write GPRs write the whole register, and the current
      ABI targets allow writing the extra words.  Closes #15.
---
 lightening/lightening.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/lightening/lightening.c b/lightening/lightening.c
index 7f42a34..ad990eb 100644
--- a/lightening/lightening.c
+++ b/lightening/lightening.c
@@ -721,21 +721,26 @@ static void
 abi_gpr_to_mem(jit_state_t *_jit, enum jit_operand_abi abi,
                jit_gpr_t base, ptrdiff_t offset, jit_gpr_t src)
 {
+  // Invariant: GPR memory destination operand sizes are rounded up to words.
+  // True for ARM, AArch64, IA32, and X86-64.  Some ABIs expect to be able to
+  // load operands from the stack via a full-word read, so we need to make sure
+  // we don't leave garbage in the high bytes of (for example) the stack slot
+  // for a uint8_t arg.
   switch (abi) {
   case JIT_OPERAND_ABI_UINT8:
   case JIT_OPERAND_ABI_INT8:
-    jit_stxi_c(_jit, offset, base, src);
+    jit_stxi(_jit, offset, base, src);
     break;
   case JIT_OPERAND_ABI_UINT16:
   case JIT_OPERAND_ABI_INT16:
-    jit_stxi_s(_jit, offset, base, src);
+    jit_stxi(_jit, offset, base, src);
     break;
   case JIT_OPERAND_ABI_UINT32:
   case JIT_OPERAND_ABI_INT32:
 #if __WORDSIZE == 32
   case JIT_OPERAND_ABI_POINTER:
 #endif
-    jit_stxi_i(_jit, offset, base, src);
+    jit_stxi(_jit, offset, base, src);
     break;
 #if __WORDSIZE == 64
   case JIT_OPERAND_ABI_UINT64: