@@ -723,6 +723,32 @@ void vrfy_flow(struct entrypoint *ep)
assert(!entry);
}
+static void adjust_phi(struct basic_block *top, struct instruction *insn)
+{
+ struct pseudo_user *pu;
+
+ FOR_EACH_PTR(insn->target->users, pu) {
+ struct instruction *user;
+ pseudo_t phi;
+
+ if (!pu)
+ continue;
+ user = pu->insn;
+ assert(user->opcode == OP_PHI);
+ FOR_EACH_PTR(user->phi_list, phi) {
+ struct instruction *phisrc;
+
+ if (phi == VOID)
+ continue;
+ phisrc = phi->def;
+ if (phisrc->bb != top)
+ continue;
+ REPLACE_CURRENT_PTR(phi, VOID);
+ kill_instruction(phisrc);
+ } END_FOR_EACH_PTR(phi);
+ } END_FOR_EACH_PTR(pu);
+}
+
void pack_basic_blocks(struct entrypoint *ep)
{
struct basic_block *bb;
@@ -804,6 +830,8 @@ out:
if (!insn->bb)
continue;
assert(insn->bb == bb);
+ if (insn->opcode == OP_PHISOURCE)
+ adjust_phi(parent, insn);
insn->bb = parent;
add_instruction(&parent->insns, insn);
} END_FOR_EACH_PTR(insn);
@@ -16,7 +16,6 @@ int select(void)
/*
* check-name: merge_bbe-adjust_phi
* check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
*
* check-output-ignore
* check-output-excludes: phisrc\\.
When merging two basic blocks, it may happen that both of theses blocks contain a phi-source for the same phi-node. In this case, only the phi-source from the bottom BB must be taken in account, it kinda overwrites the value from the top BB and the phi-source from the top BB must be ignored, in fact it must be removed. However, it is not the case and this extra phi-source creates different kind of problems. Among other things, it hinders further simplifications. For example, the following code: extern int array[2]; static inline int stupid_select(int idx) { if (idx) idx = 0; return array[idx]; } int select(void) { int d = stupid_select(-1); return d; } should boil down to a simple dereference of the array with an index of zero, like: select: load.32 %r8 <- 0[array] ret.32 %r8 but currently gives: select: phisrc.32 %phi3(idx) <- $0xffffffff phisrc.32 %phi4(idx) <- $0 phi.32 %r12(idx) <- %phi3(idx), %phi4(idx) sext.64 %r5 <- (32) %r12(idx) mul.64 %r6 <- %r5, $4 add.64 %r7 <- %r6, array load.32 %r8 <- 0[%r7] ret.32 %r8 This patch takes care of the problem by: * when merging 2 BBs, check when reaching a phi-source in the bottom BB * if one is found, look after sibling phi-sources * remove such sibling if belonging to the top BB. With this change, the code above gives: select: phisrc.32 %phi4(idx) <- $0 phi.32 %r12(idx) <- %phi4(idx) sext.64 %r5 <- (32) %r12(idx) mul.64 %r6 <- %r5, $4 add.64 %r7 <- %r6, array load.32 %r8 <- 0[%r7] ret.32 %r8 which can the be simplified into the expected result. Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> --- flow.c | 28 +++++++++++++++++++++++++ validation/optim/merge_bbe-adjust_phi.c | 1 - 2 files changed, 28 insertions(+), 1 deletion(-)