Teach ScalarEvolution to exploit min and max expressions when proving

isKnownPredicate.

The motivation for this change is to optimize away checks in loops
like this:

    limit = min(t, len)
    for (i = 0 to limit)
      if (i >= len || i < 0) throw_array_of_of_bounds();
      a[i] = ...

Differential Revision: http://reviews.llvm.org/D6635

llvm-svn: 224285

1 files changed, 453 insertions, 0 deletions

diff --git a/llvm/test/Transforms/IndVarSimplify/backedge-on-min-max.ll b/llvm/test/Transforms/IndVarSimplify/backedge-on-min-max.ll
new file mode 100644
index 00000000000..250ff9a2eca
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/backedge-on-min-max.ll
@@ -0,0 +1,453 @@
+; RUN: opt < %s -indvars -S | FileCheck %s
+
+;; --- signed ---
+
+define void @min.signed.1(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @min.signed.1
+ entry:
+  %smin.cmp = icmp slt i32 %a_len, %n
+  %smin = select i1 %smin.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp slt i32 0, %smin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp slt i32 %idx, %a_len
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp slt i32 %idx.inc, %smin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @min.signed.2(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @min.signed.2
+ entry:
+  %smin.cmp = icmp slt i32 %a_len, %n
+  %smin = select i1 %smin.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp slt i32 0, %smin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp sgt i32 %a_len, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp slt i32 %idx.inc, %smin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @min.signed.3(i32* %a, i32 %n) {
+; CHECK-LABEL: @min.signed.3
+ entry:
+  %smin.cmp = icmp slt i32 42, %n
+  %smin = select i1 %smin.cmp, i32 42, i32 %n
+  %entry.cond = icmp slt i32 0, %smin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp slt i32 %idx, 42
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp slt i32 %idx.inc, %smin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @min.signed.4(i32* %a, i32 %n) {
+; CHECK-LABEL: @min.signed.4
+ entry:
+  %smin.cmp = icmp slt i32 42, %n
+  %smin = select i1 %smin.cmp, i32 42, i32 %n
+  %entry.cond = icmp slt i32 0, %smin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp sgt i32 42, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp slt i32 %idx.inc, %smin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.signed.1(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @max.signed.1
+ entry:
+  %smax.cmp = icmp sgt i32 %a_len, %n
+  %smax = select i1 %smax.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp sgt i32 0, %smax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp sgt i32 %idx, %a_len
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp sgt i32 %idx.inc, %smax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.signed.2(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @max.signed.2
+ entry:
+  %smax.cmp = icmp sgt i32 %a_len, %n
+  %smax = select i1 %smax.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp sgt i32 0, %smax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp slt i32 %a_len, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp sgt i32 %idx.inc, %smax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.signed.3(i32* %a, i32 %n, i32 %init) {
+; CHECK-LABEL: @max.signed.3
+ entry:
+  %smax.cmp = icmp sgt i32 42, %n
+  %smax = select i1 %smax.cmp, i32 42, i32 %n
+  %entry.cond = icmp sgt i32 %init, %smax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ %init, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp sgt i32 %idx, 42
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp sgt i32 %idx.inc, %smax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.signed.4(i32* %a, i32 %n, i32 %init) {
+; CHECK-LABEL: @max.signed.4
+ entry:
+  %smax.cmp = icmp sgt i32 42, %n
+  %smax = select i1 %smax.cmp, i32 42, i32 %n
+  %entry.cond = icmp sgt i32 %init, %smax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ %init, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp slt i32 42, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp sgt i32 %idx.inc, %smax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+;; --- unsigned ---
+
+define void @min.unsigned.1(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @min.unsigned.1
+ entry:
+  %umin.cmp = icmp ult i32 %a_len, %n
+  %umin = select i1 %umin.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp ult i32 5, %umin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 5, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ult i32 %idx, %a_len
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ult i32 %idx.inc, %umin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @min.unsigned.2(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @min.unsigned.2
+ entry:
+  %umin.cmp = icmp ult i32 %a_len, %n
+  %umin = select i1 %umin.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp ult i32 5, %umin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 5, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ugt i32 %a_len, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ult i32 %idx.inc, %umin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @min.unsigned.3(i32* %a, i32 %n) {
+; CHECK-LABEL: @min.unsigned.3
+ entry:
+  %umin.cmp = icmp ult i32 42, %n
+  %umin = select i1 %umin.cmp, i32 42, i32 %n
+  %entry.cond = icmp ult i32 5, %umin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 5, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ult i32 %idx, 42
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ult i32 %idx.inc, %umin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @min.unsigned.4(i32* %a, i32 %n) {
+; CHECK-LABEL: @min.unsigned.4
+ entry:
+  %umin.cmp = icmp ult i32 42, %n
+  %umin = select i1 %umin.cmp, i32 42, i32 %n
+  %entry.cond = icmp ult i32 5, %umin
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 5, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ugt i32 42, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ult i32 %idx.inc, %umin
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.unsigned.1(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @max.unsigned.1
+ entry:
+  %umax.cmp = icmp ugt i32 %a_len, %n
+  %umax = select i1 %umax.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp ugt i32 5, %umax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 5, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ugt i32 %idx, %a_len
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ugt i32 %idx.inc, %umax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.unsigned.2(i32* %a, i32 %a_len, i32 %n) {
+; CHECK-LABEL: @max.unsigned.2
+ entry:
+  %umax.cmp = icmp ugt i32 %a_len, %n
+  %umax = select i1 %umax.cmp, i32 %a_len, i32 %n
+  %entry.cond = icmp ugt i32 5, %umax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 5, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ult i32 %a_len, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ugt i32 %idx.inc, %umax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.unsigned.3(i32* %a, i32 %n, i32 %init) {
+; CHECK-LABEL: @max.unsigned.3
+ entry:
+  %umax.cmp = icmp ugt i32 42, %n
+  %umax = select i1 %umax.cmp, i32 42, i32 %n
+  %entry.cond = icmp ugt i32 %init, %umax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ %init, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ugt i32 %idx, 42
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ugt i32 %idx.inc, %umax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @max.unsigned.4(i32* %a, i32 %n, i32 %init) {
+; CHECK-LABEL: @max.unsigned.4
+ entry:
+  %umax.cmp = icmp ugt i32 42, %n
+  %umax = select i1 %umax.cmp, i32 42, i32 %n
+  %entry.cond = icmp ugt i32 %init, %umax
+  br i1 %entry.cond, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ %init, %entry ], [ %idx.inc, %latch ]
+  %idx.inc = add i32 %idx, 1
+  %in.bounds = icmp ult i32 42, %idx
+  br i1 %in.bounds, label %ok, label %latch
+; CHECK: br i1 true, label %ok, label %latch
+
+ ok:
+  %addr = getelementptr i32* %a, i32 %idx
+  store i32 %idx, i32* %addr
+  br label %latch
+
+ latch:
+  %be.cond = icmp ugt i32 %idx.inc, %umax
+  br i1 %be.cond, label %loop, label %exit
+
+ exit:
+  ret void
+}