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llvm-mirror/test/Transforms/SCCP/domtree-update.ll
Nikita Popov 74624d8649 Reapply [SCCP] Directly remove non-feasible edges
Reapply with DTU update moved after CFG update, which is a
requirement of the API.

-----

Non-feasible control-flow edges are currently removed by replacing
the branch condition with a constant and then calling
ConstantFoldTerminator. This happens in a rather roundabout manner,
by inspecting the users (effectively: predecessors) of unreachable
blocks, and further complicated by the need to explicitly materialize
the condition for "forced" edges. I would like to extend SCCP to
discard switch conditions that are non-feasible based on range
information, but this is incompatible with the current approach
(as there is no single constant we could use.)

Instead, this patch explicitly removes non-feasible edges. It
currently only needs to handle the case where there is a single
feasible edge. The llvm_unreachable() branch will need to be
implemented for the aforementioned switch improvement.

Differential Revision: https://reviews.llvm.org/D84264
2020-07-25 14:52:35 +02:00

42 lines
1.3 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -ipsccp < %s | FileCheck %s
; RUN: opt -S -passes='ipsccp,function(verify<domtree>)' < %s | FileCheck %s
; DTU should not crash.
define i32 @test() {
; CHECK-LABEL: @test(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: br label [[IF_THEN2:%.*]]
; CHECK: if.then2:
; CHECK-NEXT: br label [[FOR_INC:%.*]]
; CHECK: for.inc:
; CHECK-NEXT: unreachable
;
entry:
br label %for.body
for.body: ; preds = %entry
br i1 true, label %if.then2, label %if.else
if.then2: ; preds = %for.body
br label %for.inc
if.else: ; preds = %for.body
br i1 undef, label %lor.rhs, label %if.then19.critedge
lor.rhs: ; preds = %if.else
br i1 undef, label %if.then19, label %for.inc
if.then19.critedge: ; preds = %if.else
br label %if.then19
if.then19: ; preds = %if.then19.critedge, %lor.rhs
unreachable
for.inc: ; preds = %lor.rhs, %if.then2
unreachable
}