[SCEV] Use guards to prove predicates
We can use calls to @llvm.experimental.guard to prove predicates,
relying on the fact that in all locations domianted by a call to
@llvm.experimental.guard the predicate it is guarding is known to be
true.
llvm-svn: 268997
diff --git a/llvm/test/Analysis/ScalarEvolution/guards.ll b/llvm/test/Analysis/ScalarEvolution/guards.ll
new file mode 100644
index 0000000..52ad4dc
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/guards.ll
@@ -0,0 +1,141 @@
+; RUN: opt -S -indvars < %s | FileCheck %s
+
+; Check that SCEV is able to recognize and use guards to prove
+; conditions gaurding loop entries and backedges. This isn't intended
+; to be a comprehensive test of SCEV's simplification capabilities,
+; tests directly testing e.g. if SCEV can elide a sext should go
+; elsewhere.
+
+target datalayout = "n8:16:32:64"
+
+declare void @llvm.experimental.guard(i1, ...)
+
+define void @test_1(i1* %cond_buf, i32* %len_buf) {
+; CHECK-LABEL: @test_1(
+entry:
+ %len = load i32, i32* %len_buf, !range !{i32 1, i32 2147483648}
+ br label %loop
+
+loop:
+; CHECK: loop:
+; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 true) [ "deopt"() ]
+; CHECK: %iv.inc.cmp = icmp slt i32 %iv.inc, %len
+; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
+; CHECK: leave:
+
+ %iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
+ %iv.inc = add i32 %iv, 1
+
+ %iv.cmp = icmp slt i32 %iv, %len
+ call void(i1, ...) @llvm.experimental.guard(i1 %iv.cmp) [ "deopt"() ]
+
+ %iv.inc.cmp = icmp slt i32 %iv.inc, %len
+ call void(i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
+
+ %becond = load volatile i1, i1* %cond_buf
+ br i1 %becond, label %loop, label %leave
+
+leave:
+ ret void
+}
+
+define void @test_2(i32 %n, i32* %len_buf) {
+; CHECK-LABEL: @test_2(
+; CHECK: [[LEN_SEXT:%[^ ]+]] = sext i32 %len to i64
+; CHECK: br label %loop
+
+entry:
+ %len = load i32, i32* %len_buf, !range !{i32 0, i32 2147483648}
+ br label %loop
+
+loop:
+; CHECK: loop:
+; CHECK: %indvars.iv = phi i64 [ %indvars.iv.next, %loop ], [ 0, %entry ]
+; CHECK: %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+; CHECK: %iv.inc.cmp = icmp slt i64 %indvars.iv.next, [[LEN_SEXT]]
+; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
+; CHECK: leave:
+
+ %iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
+ %iv.inc = add i32 %iv, 1
+
+ %iv.sext = sext i32 %iv to i64
+
+ %iv.inc.cmp = icmp slt i32 %iv.inc, %len
+ call void(i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
+
+ %becond = icmp ne i32 %iv, %n
+ br i1 %becond, label %loop, label %leave
+
+leave:
+ ret void
+}
+
+define void @test_3(i1* %cond_buf, i32* %len_buf) {
+; CHECK-LABEL: @test_3(
+
+entry:
+ %len = load i32, i32* %len_buf
+ %entry.cond = icmp sgt i32 %len, 0
+ call void(i1, ...) @llvm.experimental.guard(i1 %entry.cond) [ "deopt"() ]
+ br label %loop
+
+loop:
+; CHECK: loop:
+; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 true) [ "deopt"() ]
+; CHECK: %iv.inc.cmp = icmp slt i32 %iv.inc, %len
+; CHECK: call void (i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
+; CHECK: leave:
+ %iv = phi i32 [ 0, %entry ], [ %iv.inc, %loop ]
+ %iv.inc = add i32 %iv, 1
+
+ %iv.cmp = icmp slt i32 %iv, %len
+ call void(i1, ...) @llvm.experimental.guard(i1 %iv.cmp) [ "deopt"() ]
+
+ %iv.inc.cmp = icmp slt i32 %iv.inc, %len
+ call void(i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
+
+ %becond = load volatile i1, i1* %cond_buf
+ br i1 %becond, label %loop, label %leave
+
+leave:
+ ret void
+}
+
+define void @test_4(i1* %cond_buf, i32* %len_buf) {
+; CHECK-LABEL: @test_4(
+
+entry:
+ %len = load i32, i32* %len_buf
+ %entry.cond = icmp sgt i32 %len, 0
+ call void(i1, ...) @llvm.experimental.guard(i1 %entry.cond) [ "deopt"() ]
+ br label %loop
+
+loop:
+ %iv = phi i32 [ 0, %entry ], [ %iv.inc, %be ]
+ %iv.inc = add i32 %iv, 1
+
+ %cond = load volatile i1, i1* %cond_buf
+ br i1 %cond, label %left, label %be
+
+left:
+ ; Does not dominate the backedge, so cannot be used in the inductive proof
+ %iv.inc.cmp = icmp slt i32 %iv.inc, %len
+ call void(i1, ...) @llvm.experimental.guard(i1 %iv.inc.cmp) [ "deopt"() ]
+ br label %be
+
+be:
+; CHECK: be:
+; CHECK-NEXT: %iv.cmp = icmp slt i32 %iv, %len
+; CHECK-NEXT: call void (i1, ...) @llvm.experimental.guard(i1 %iv.cmp) [ "deopt"() ]
+; CHECK: leave:
+
+ %iv.cmp = icmp slt i32 %iv, %len
+ call void(i1, ...) @llvm.experimental.guard(i1 %iv.cmp) [ "deopt"() ]
+
+ %becond = load volatile i1, i1* %cond_buf
+ br i1 %becond, label %loop, label %leave
+
+leave:
+ ret void
+}