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target/i386: tcg: simplify computation of AF after INC/DEC

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No difference in generated code, but the XOR-based formula is
easily understood on its own.  This will make more sense once
ADD/SUB stop using dst^src1^src2 to compute AF.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-04-03 14:06:37 +02:00
parent 9a688e70bd
commit 3fec86e95c
1 changed files with 2 additions and 8 deletions
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10
target/i386/tcg/cc_helper_template.h.inc
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@ -175,13 +175,10 @@ static uint32_t glue(compute_all_logic, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
static uint32_t glue(compute_all_inc, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
{
uint32_t cf, pf, af, zf, sf, of;
DATA_TYPE src2;
cf = src1;
src1 = dst - 1;
src2 = 1;
pf = compute_pf(dst);
af = (dst ^ src1 ^ src2) & CC_A;
af = (dst ^ (dst - 1)) & CC_A; /* bits 0..3 are all clear */
zf = (dst == 0) * CC_Z;
sf = lshift(dst, 8 - DATA_BITS) & CC_S;
of = (dst == SIGN_MASK) * CC_O;
@ -191,13 +188,10 @@ static uint32_t glue(compute_all_inc, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
static uint32_t glue(compute_all_dec, SUFFIX)(DATA_TYPE dst, DATA_TYPE src1)
{
uint32_t cf, pf, af, zf, sf, of;
DATA_TYPE src2;
cf = src1;
src1 = dst + 1;
src2 = 1;
pf = compute_pf(dst);
af = (dst ^ src1 ^ src2) & CC_A;
af = (dst ^ (dst + 1)) & CC_A; /* bits 0..3 are all set */
zf = (dst == 0) * CC_Z;
sf = lshift(dst, 8 - DATA_BITS) & CC_S;
of = (dst == SIGN_MASK - 1) * CC_O;