Move Instruction::isSafeToSpeculativelyExecute out of VMCore and

into Analysis as a standalone function, since there's no need for
it to be in VMCore. Also, update it to use isKnownNonZero and
other goodies available in Analysis, making it more precise,
enabling more aggressive optimization.

llvm-svn: 146610

1 files changed, 167 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LICM/speculate.ll b/llvm/test/Transforms/LICM/speculate.ll
new file mode 100644
index 00000000000..507b193e6b1
--- /dev/null
+++ b/llvm/test/Transforms/LICM/speculate.ll
@@ -0,0 +1,167 @@
+; RUN: opt -S -licm < %s | FileCheck %s
+
+; UDiv is safe to speculate if the denominator is known non-zero.
+
+; CHECK: @safe_udiv
+; CHECK:      %div = udiv i64 %x, %or
+; CHECK-NEXT: br label %for.body
+
+define void @safe_udiv(i64 %x, i64 %m, i64 %n, i32* %p, i64* %q) nounwind {
+entry:
+  %or = or i64 %m, 1
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.inc
+  %i.02 = phi i64 [ %inc, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %p, i64 %i.02
+  %0 = load i32* %arrayidx, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %for.inc, label %if.then
+
+if.then:                                          ; preds = %for.body
+  %div = udiv i64 %x, %or
+  %arrayidx1 = getelementptr inbounds i64* %q, i64 %i.02
+  store i64 %div, i64* %arrayidx1, align 8
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then, %for.body
+  %inc = add i64 %i.02, 1
+  %cmp = icmp slt i64 %inc, %n
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; UDiv is unsafe to speculate if the denominator is not known non-zero.
+
+; CHECK: @unsafe_udiv
+; CHECK-NOT:  udiv
+; CHECK: for.body:
+
+define void @unsafe_udiv(i64 %x, i64 %m, i64 %n, i32* %p, i64* %q) nounwind {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.inc
+  %i.02 = phi i64 [ %inc, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %p, i64 %i.02
+  %0 = load i32* %arrayidx, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %for.inc, label %if.then
+
+if.then:                                          ; preds = %for.body
+  %div = udiv i64 %x, %m
+  %arrayidx1 = getelementptr inbounds i64* %q, i64 %i.02
+  store i64 %div, i64* %arrayidx1, align 8
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then, %for.body
+  %inc = add i64 %i.02, 1
+  %cmp = icmp slt i64 %inc, %n
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; SDiv is safe to speculate if the denominator is known non-zero and
+; known to have at least one zero bit.
+
+; CHECK: @safe_sdiv
+; CHECK:      %div = sdiv i64 %x, %or
+; CHECK-NEXT: br label %for.body
+
+define void @safe_sdiv(i64 %x, i64 %m, i64 %n, i32* %p, i64* %q) nounwind {
+entry:
+  %and = and i64 %m, -3
+  %or = or i64 %and, 1
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.inc
+  %i.02 = phi i64 [ %inc, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %p, i64 %i.02
+  %0 = load i32* %arrayidx, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %for.inc, label %if.then
+
+if.then:                                          ; preds = %for.body
+  %div = sdiv i64 %x, %or
+  %arrayidx1 = getelementptr inbounds i64* %q, i64 %i.02
+  store i64 %div, i64* %arrayidx1, align 8
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then, %for.body
+  %inc = add i64 %i.02, 1
+  %cmp = icmp slt i64 %inc, %n
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; SDiv is unsafe to speculate if the denominator is not known non-zero.
+
+; CHECK: @unsafe_sdiv_a
+; CHECK-NOT:  sdiv
+; CHECK: for.body:
+
+define void @unsafe_sdiv_a(i64 %x, i64 %m, i64 %n, i32* %p, i64* %q) nounwind {
+entry:
+  %or = or i64 %m, 1
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.inc
+  %i.02 = phi i64 [ %inc, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %p, i64 %i.02
+  %0 = load i32* %arrayidx, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %for.inc, label %if.then
+
+if.then:                                          ; preds = %for.body
+  %div = sdiv i64 %x, %or
+  %arrayidx1 = getelementptr inbounds i64* %q, i64 %i.02
+  store i64 %div, i64* %arrayidx1, align 8
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then, %for.body
+  %inc = add i64 %i.02, 1
+  %cmp = icmp slt i64 %inc, %n
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}
+
+; SDiv is unsafe to speculate if the denominator is not known to have a zero bit.
+
+; CHECK: @unsafe_sdiv_b
+; CHECK-NOT:  sdiv
+; CHECK: for.body:
+
+define void @unsafe_sdiv_b(i64 %x, i64 %m, i64 %n, i32* %p, i64* %q) nounwind {
+entry:
+  %and = and i64 %m, -3
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.inc
+  %i.02 = phi i64 [ %inc, %for.inc ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i32* %p, i64 %i.02
+  %0 = load i32* %arrayidx, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %for.inc, label %if.then
+
+if.then:                                          ; preds = %for.body
+  %div = sdiv i64 %x, %and
+  %arrayidx1 = getelementptr inbounds i64* %q, i64 %i.02
+  store i64 %div, i64* %arrayidx1, align 8
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then, %for.body
+  %inc = add i64 %i.02, 1
+  %cmp = icmp slt i64 %inc, %n
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.inc, %entry
+  ret void
+}