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authorAurelien Jarno <aurelien@aurel32.net>2015-07-10 18:03:31 +0200
committerRichard Henderson <rth@twiddle.net>2015-08-24 11:10:08 -0700
commit29f3ff8d6cbc28f79933aeaa25805408d0984a8f (patch)
tree70c3174b701cace8d606a50d69c102bb44e0541a /tcg/optimize.c
parenta30878e708c2149ce07d709a8b62edd944628449 (diff)
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tcg/optimize: fix constant signedness
By convention, on a 64-bit host TCG internally stores 32-bit constants as sign-extended. This is not the case in the optimizer when a 32-bit constant is folded. This doesn't seem to have more consequences than suboptimal code generation. For instance the x86 backend assumes sign-extended constants, and in some rare cases uses a 32-bit unsigned immediate 0xffffffff instead of a 8-bit signed immediate 0xff for the constant -1. This is with a ppc guest: before ------ ---- 0x9f29cc movi_i32 tmp1,$0xffffffff movi_i32 tmp2,$0x0 add2_i32 tmp0,CA,CA,tmp2,r6,tmp2 add2_i32 tmp0,CA,tmp0,CA,tmp1,tmp2 mov_i32 r10,tmp0 0x7fd8c7dfe90c: xor %ebp,%ebp 0x7fd8c7dfe90e: mov %ebp,%r11d 0x7fd8c7dfe911: mov 0x18(%r14),%r9d 0x7fd8c7dfe915: add %r9d,%r10d 0x7fd8c7dfe918: adc %ebp,%r11d 0x7fd8c7dfe91b: add $0xffffffff,%r10d 0x7fd8c7dfe922: adc %ebp,%r11d 0x7fd8c7dfe925: mov %r11d,0x134(%r14) 0x7fd8c7dfe92c: mov %r10d,0x28(%r14) after ----- ---- 0x9f29cc movi_i32 tmp1,$0xffffffffffffffff movi_i32 tmp2,$0x0 add2_i32 tmp0,CA,CA,tmp2,r6,tmp2 add2_i32 tmp0,CA,tmp0,CA,tmp1,tmp2 mov_i32 r10,tmp0 0x7f37010d490c: xor %ebp,%ebp 0x7f37010d490e: mov %ebp,%r11d 0x7f37010d4911: mov 0x18(%r14),%r9d 0x7f37010d4915: add %r9d,%r10d 0x7f37010d4918: adc %ebp,%r11d 0x7f37010d491b: add $0xffffffffffffffff,%r10d 0x7f37010d491f: adc %ebp,%r11d 0x7f37010d4922: mov %r11d,0x134(%r14) 0x7f37010d4929: mov %r10d,0x28(%r14) Signed-off-by: Aurelien Jarno <aurelien@aurel32.net> Message-Id: <1436544211-2769-2-git-send-email-aurelien@aurel32.net> Signed-off-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'tcg/optimize.c')
-rw-r--r--tcg/optimize.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/tcg/optimize.c b/tcg/optimize.c
index 18283cf..cd0e793 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -395,7 +395,7 @@ static TCGArg do_constant_folding(TCGOpcode op, TCGArg x, TCGArg y)
{
TCGArg res = do_constant_folding_2(op, x, y);
if (op_bits(op) == 32) {
- res &= 0xffffffff;
+ res = (int32_t)res;
}
return res;
}
@@ -1128,8 +1128,8 @@ void tcg_optimize(TCGContext *s)
rl = args[0];
rh = args[1];
- tcg_opt_gen_movi(s, op, args, rl, (uint32_t)a);
- tcg_opt_gen_movi(s, op2, args2, rh, (uint32_t)(a >> 32));
+ tcg_opt_gen_movi(s, op, args, rl, (int32_t)a);
+ tcg_opt_gen_movi(s, op2, args2, rh, (int32_t)(a >> 32));
/* We've done all we need to do with the movi. Skip it. */
oi_next = op2->next;
@@ -1149,8 +1149,8 @@ void tcg_optimize(TCGContext *s)
rl = args[0];
rh = args[1];
- tcg_opt_gen_movi(s, op, args, rl, (uint32_t)r);
- tcg_opt_gen_movi(s, op2, args2, rh, (uint32_t)(r >> 32));
+ tcg_opt_gen_movi(s, op, args, rl, (int32_t)r);
+ tcg_opt_gen_movi(s, op2, args2, rh, (int32_t)(r >> 32));
/* We've done all we need to do with the movi. Skip it. */
oi_next = op2->next;