On Thu, Sep 07, 2017 at 12:05:58AM +0100, Dibyendu Majumdar wrote:
> Hi,
>
> I recently found another test case that fails:
>
> static int test_do(void) {
> int a = 0;
> int count = 27;
> switch (count % 8) {
> case 0: do { a++;
> case 7: a++;
> case 6: a++;
> case 5: a++;
> case 4: a++;
> case 3: a++;
> case 2: a++;
> case 1: a++;
> } while ((count -= 8) > 0);
> }
> if (27 != a) return 1;
> return 0;
> }
Ah, a Duff device with a constant. A smart compiler could
optimize it away entirely.
In our case, the simplification of the switch (called once
and with a constant value) leave all the case's phi-node
incorrect (but the one for 3).
The following patch should solve it but I would like to have a
better way to do the matching between the BB and the phi-operands.
With this I get the follwing result, which look correct:
foo:
.L0:
<entry-point>
phisrc.32 %phi13(a) <- $0
phisrc.32 %phi21(count) <- $27
br .L7
.L6:
add.32 %r12 <- %r18, $5
phisrc.32 %phi14(a) <- %r12
phisrc.32 %phi32(count) <- %r21
br .L7
.L7:
phi.32 %r34(a) <- %phi13(a), %phi14(a)
phi.32 %r37(count) <- %phi21(count), %phi32(count)
add.32 %r18 <- %r34(a), $3
add.32 %r21 <- %r37(count), $-8
setgt.32 %r23 <- %r21, $0
cbr %r23, .L6, .L1
.L1:
setne.32 %r25 <- %r18, $27
ret.32 %r25
------------------------------------------------------------------------
>From 275d1ae2c2e187783d1d095d5f9f5950bc360be9 Mon Sep 17 00:00:00 2001
From: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
Date: Thu, 7 Sep 2017 03:18:30 +0200
Subject: [PATCH] fix remove_parent()
---
linearize.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 45 insertions(+), 1 deletion(-)
diff --git a/linearize.c b/linearize.c
index eabf8575a..eb6b53a0a 100644
--- a/linearize.c
+++ b/linearize.c
@@ -649,9 +649,53 @@ static void set_activeblock(struct entrypoint *ep, struct basic_block *bb)
add_bb(&ep->bbs, bb);
}
+
+static void remove_nth_phisource(struct instruction *insn, int nth)
+{
+ pseudo_t src;
+ int i = 0;
+
+ FOR_EACH_PTR(insn->phi_list, src) {
+ if (++i < nth)
+ continue;
+ *THIS_ADDRESS(src) = VOID;
+ return;
+ } END_FOR_EACH_PTR(src);
+ assert(0);
+}
+
+static void remove_nth_phisources(struct basic_block *bb, int nth)
+{
+ struct instruction *insn;
+
+ FOR_EACH_PTR(bb->insns, insn) {
+ if (!insn->bb)
+ continue;
+ if (insn->opcode != OP_PHI)
+ break;
+
+ remove_nth_phisource(insn, nth);
+ } END_FOR_EACH_PTR(insn);
+}
+
static void remove_parent(struct basic_block *child, struct basic_block *parent)
{
- remove_bb_from_list(&child->parents, parent, 1);
+ struct basic_block *bb;
+ int nth = 0;
+
+ FOR_EACH_PTR(child->parents, bb) {
+ nth++;
+
+ if (bb != parent)
+ continue;
+
+ DELETE_CURRENT_PTR(bb);
+ goto found;
+ } END_FOR_EACH_PTR(bb);
+ assert(0); // should never be reached
+
+found:
+ remove_nth_phisources(child, nth);
if (!child->parents)
repeat_phase |= REPEAT_CFG_CLEANUP;
}
--
2.14.0
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