Currently kill_instruction() doesn't do anything with the
sources of OP_PHI instructions. But when these instructions
are removed the 'usage' of the associated sources must also
be removed. This is not done and as result the instructions
producing the phi-sources are not optimized away as expected.
This patch fixes that by calling clear_phi() when killing a
phi-instruction.
For example, when looking at the output of test-linearize,
the following function:
void foo(int a, int *b, unsigned int g);
void foo(int a, int *b, unsigned int g)
{
int d = 0;
if ((!a || *b) && g)
d = 16;
else
d = 8;
}
gives this output without the patch:
foo:
br %arg1, .L1, .L2
.L1:
phisrc.32 %phi1 <- $1
br .L3
.L2:
load.32 %r3 <- 0[%arg2]
phisrc.32 %phi2 <- %r3
br .L3
.L3:
ret
The 'phisrc' instructions are obviously unneeded but nevertheless present.
With the patch, the output is much closer to what's expected:
foo:
br %arg1, .L3, .L2
.L2:
load.32 %r3 <- 0[%arg2]
br .L3
.L3:
ret
Note 1) The 'load' instruction is also dead and should have been removed
but it's separate problem.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 1 +
validation/kill-phi-node.c | 18 ++++++++++++++++++
2 files changed, 19 insertions(+)
create mode 100644 validation/kill-phi-node.c
diff --git a/simplify.c b/simplify.c
index d07ca1b1..421b28f2 100644
--- a/simplify.c
+++ b/simplify.c
@@ -203,6 +203,7 @@ void kill_instruction(struct instruction *insn)
return;
case OP_PHI:
+ clear_phi(insn);
insn->bb = NULL;
repeat_phase |= REPEAT_CSE;
return;
diff --git a/validation/kill-phi-node.c b/validation/kill-phi-node.c
new file mode 100644
index 00000000..88de9f96
--- /dev/null
+++ b/validation/kill-phi-node.c
@@ -0,0 +1,18 @@
+void foo(int a, int *b, unsigned int g);
+void foo(int a, int *b, unsigned int g)
+{
+ int d = 0;
+
+ if ((!a || *b) && g)
+ d = 16;
+ else
+ d = 8;
+}
+
+/*
+ * check-name: kill-phi-node
+ * check-command: test-linearize $file
+ *
+ * check-output-ignore
+ * check-output-excludes: phisrc\\.
+ */
--
2.10.2
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