When an instruction is replaced by a pseudo, the 'usage' of its
operands should be removed too but it's not the case.
The fix consists in calling kill_use() for each operands after
the pseudo is replaced.
Not all types of instruction are considered, only those which
can be replaced by a pseudo.
The following example illustrate the situation. When looking at
the output of test-linearize, the following function:
static int kill_add(int a, int b)
{
return (a + b) && 0;
}
without the patch, gives this output:
kill_add:
add.32 %r3 <- %arg1, %arg2
ret.32 $0
The 'add' instruction is obviously unneeded but nevertheless present.
Before any optimization the code was something like:
kill_add:
add.32 %r3 <- %arg1, %arg2
and_bool.32 %r4 <- %r3, $0
ret.32 %r4
During the simplification phase, the result of the 'and' instruction (%r4)
have been replaced by '0' and the instruction itself is discarded.
But '%r3' usage has not been adjusted and the further phases are not
aware that '%r3' is not needed anymore and so the 'add' instruction is kept
while not needed by anything.
With the patch the 'add' instruction is correctly discarded, giving the
expected output:
kill_add:
ret.32 $0
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
simplify.c | 20 +++++++++++++++
validation/kill-replaced-insn.c | 54 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 74 insertions(+)
create mode 100644 validation/kill-replaced-insn.c
diff --git a/simplify.c b/simplify.c
index 3dea03b5e..ed41e441a 100644
--- a/simplify.c
+++ b/simplify.c
@@ -253,6 +253,26 @@ static inline int constant(pseudo_t pseudo)
static int replace_with_pseudo(struct instruction *insn, pseudo_t pseudo)
{
convert_instruction_target(insn, pseudo);
+
+ switch (insn->opcode) {
+ case OP_SEL:
+ case OP_RANGE:
+ kill_use(&insn->src3);
+ case OP_BINARY ... OP_BINCMP_END:
+ kill_use(&insn->src2);
+ case OP_NOT:
+ case OP_NEG:
+ case OP_SYMADDR:
+ case OP_CAST:
+ case OP_SCAST:
+ case OP_FPCAST:
+ case OP_PTRCAST:
+ kill_use(&insn->src1);
+ break;
+
+ default:
+ assert(0);
+ }
insn->bb = NULL;
return REPEAT_CSE;
}
diff --git a/validation/kill-replaced-insn.c b/validation/kill-replaced-insn.c
new file mode 100644
index 000000000..be031b6c1
--- /dev/null
+++ b/validation/kill-replaced-insn.c
@@ -0,0 +1,54 @@
+// See if the replaced operation is effectively killed or not
+
+static int kill_add(int a, int b)
+{
+ return (a + b) && 0;
+}
+
+static int kill_scast(short a)
+{
+ return ((int) a) && 0;
+}
+
+static int kill_ucast(unsigned char a)
+{
+ return ((int) a) && 0;
+}
+
+static int kill_pcast(int *a)
+{
+ return ((void*) a) && 0;
+}
+
+static int kill_fcast(double a)
+{
+ return ((int) a) && 0;
+}
+
+static int kill_select(int a)
+{
+ return (a ? 1 : 0) && 0;
+}
+
+static int kill_load(int *a)
+{
+ return *a && 0;
+}
+
+static int kill_store(int *a)
+{
+ return (*a = 1) && 0;
+}
+
+/*
+ * check-name: kill-replaced-insn
+ * check-command: test-linearize $file
+ *
+ * check-output-ignore
+ * check-output-excludes: add\\.
+ * check-output-excludes: scast\\.
+ * check-output-excludes: \\<cast\\.
+ * check-output-excludes: ptrcast\\.
+ * check-output-excludes: fpcast\\.
+ * check-output-excludes: sel\\.
+ */
--
2.11.0
--
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