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[Qemu-devel] [PATCH 5/8] tcg/optimize: Handle known-zeros masks for ANDC


From: Richard Henderson
Subject: [Qemu-devel] [PATCH 5/8] tcg/optimize: Handle known-zeros masks for ANDC
Date: Fri, 31 Jan 2014 08:47:00 -0600

Signed-off-by: Richard Henderson <address@hidden>
---
 tcg/optimize.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tcg/optimize.c b/tcg/optimize.c
index d3b099a..3291a08 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -727,6 +727,17 @@ static TCGArg *tcg_constant_folding(TCGContext *s, 
uint16_t *tcg_opc_ptr,
             mask = temps[args[1]].mask & mask;
             break;
 
+        CASE_OP_32_64(andc):
+            /* Known-zeros does not imply known-ones.  Therefore unless
+               args[2] is constant, we can't infer anything from it.  */
+            if (temps[args[2]].state == TCG_TEMP_CONST) {
+                mask = ~temps[args[2]].mask;
+                goto and_const;
+            }
+            /* But we certainly know nothing outside args[1] may be set. */
+            mask = temps[args[1]].mask;
+            break;
+
         case INDEX_op_sar_i32:
             if (temps[args[2]].state == TCG_TEMP_CONST) {
                 mask = (int32_t)temps[args[1]].mask >> temps[args[2]].val;
-- 
1.8.5.3




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