[IRCE] Support half-range checks.

This change to IRCE gets it to recognize "half" range checks.  Half
range checks are range checks that only either check if the index is
`slt` some positive integer ("length") or if the index is `sge` `0`.

The range solver does not try to be clever / aggressive about solving
half-range checks -- it transforms "I < L" to "0 <= I < L" and "0 <= I"
to "0 <= I < INT_SMAX".  This is safe, but not always optimal.

llvm-svn: 232444

2 files changed, 74 insertions, 0 deletions

diff --git a/llvm/test/Transforms/IRCE/only-lower-check.ll b/llvm/test/Transforms/IRCE/only-lower-check.ll
new file mode 100644
index 00000000000..4cbf5da68be
--- /dev/null
+++ b/llvm/test/Transforms/IRCE/only-lower-check.ll
@@ -0,0 +1,37 @@
+; RUN: opt -debug-only=irce -irce < %s 2>&1 | FileCheck %s
+
+; CHECK: irce: loop has 1 inductive range checks:
+; CHECK-NEXT: InductiveRangeCheck:
+; CHECK-NEXT:   Kind: RANGE_CHECK_LOWER
+; CHECK-NEXT:   Offset: (-1 + %n)  Scale: -1  Length: (null)
+; CHECK-NEXT:   Branch:   br i1 %abc, label %in.bounds, label %out.of.bounds
+; CHECK-NEXT: irce: in function only_lower_check: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
+
+define void @only_lower_check(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
+ entry:
+  %len = load i32, i32* %a_len_ptr, !range !0
+  %first.itr.check = icmp sgt i32 %n, 0
+  %start = sub i32 %n, 1
+  br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ %start, %entry ] , [ %idx.dec, %in.bounds ]
+  %idx.dec = sub i32 %idx, 1
+  %abc = icmp sge i32 %idx, 0
+  br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+  %addr = getelementptr i32, i32* %arr, i32 %idx
+  store i32 0, i32* %addr
+  %next = icmp sgt i32 %idx.dec, -1
+  br i1 %next, label %loop, label %exit
+
+ out.of.bounds:
+  ret void
+
+ exit:
+  ret void
+}
+
+!0 = !{i32 0, i32 2147483647}
+!1 = !{!"branch_weights", i32 64, i32 4}
diff --git a/llvm/test/Transforms/IRCE/only-upper-check.ll b/llvm/test/Transforms/IRCE/only-upper-check.ll
new file mode 100644
index 00000000000..eb184083d29
--- /dev/null
+++ b/llvm/test/Transforms/IRCE/only-upper-check.ll
@@ -0,0 +1,37 @@
+; RUN: opt -irce -debug-only=irce %s -S 2>&1 | FileCheck %s
+
+; CHECK: irce: loop has 1 inductive range checks:
+; CHECK-NEXT:InductiveRangeCheck:
+; CHECK-NEXT:  Kind: RANGE_CHECK_UPPER
+; CHECK-NEXT:  Offset: %offset  Scale: 1  Length:   %len = load i32, i32* %a_len_ptr, !range !0
+; CHECK-NEXT:  Branch:   br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+; CHECK-NEXT: irce: in function incrementing: constrained Loop at depth 1 containing: %loop<header><exiting>,%in.bounds<latch><exiting>
+
+define void @incrementing(i32 *%arr, i32 *%a_len_ptr, i32 %n, i32 %offset) {
+ entry:
+  %len = load i32, i32* %a_len_ptr, !range !0
+  %first.itr.check = icmp sgt i32 %n, 0
+  br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ] , [ %idx.next, %in.bounds ]
+  %idx.next = add i32 %idx, 1
+  %array.idx = add i32 %idx, %offset
+  %abc = icmp slt i32 %array.idx, %len
+  br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+  %addr = getelementptr i32, i32* %arr, i32 %array.idx
+  store i32 0, i32* %addr
+  %next = icmp slt i32 %idx.next, %n
+  br i1 %next, label %loop, label %exit
+
+ out.of.bounds:
+  ret void
+
+ exit:
+  ret void
+}
+
+!0 = !{i32 0, i32 2147483647}
+!1 = !{!"branch_weights", i32 64, i32 4}