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| author | Paolo Bonzini <pbonzini@redhat.com> | 2025-04-03 14:06:37 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2025-04-17 18:23:26 +0200 |
| commit | 3fec86e95cd44ac7db639686ef1dda143af59aea (patch) | |
| tree | a621640f36d0cd2385e84baafb98894af0899284 | |
| parent | 9a688e70bdb2f23112afeddefd91bd45674d4db9 (diff) | |
| download | qemu-3fec86e95cd44ac7db639686ef1dda143af59aea.zip qemu-3fec86e95cd44ac7db639686ef1dda143af59aea.tar.gz qemu-3fec86e95cd44ac7db639686ef1dda143af59aea.tar.bz2 | |
target/i386: tcg: simplify computation of AF after INC/DEC
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>
| -rw-r--r-- | target/i386/tcg/cc_helper_template.h.inc | 10 |
1 files changed, 2 insertions, 8 deletions
diff --git a/target/i386/tcg/cc_helper_template.h.inc b/target/i386/tcg/cc_helper_template.h.inc index 9aff16b..b821e5b 100644 --- a/target/i386/tcg/cc_helper_template.h.inc +++ b/target/i386/tcg/cc_helper_template.h.inc @@ -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; |