Add early if-conversion support to X86.

Implement the TII hooks needed by EarlyIfConversion to create cmov
instructions and estimate their latency.

Early if-conversion is still not enabled by default.

llvm-svn: 159695

1 files changed, 39 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/early-ifcvt.ll b/llvm/test/CodeGen/X86/early-ifcvt.ll
new file mode 100644
index 00000000000..ce1fe04f980
--- /dev/null
+++ b/llvm/test/CodeGen/X86/early-ifcvt.ll
@@ -0,0 +1,39 @@
+; RUN: llc < %s -enable-early-ifcvt -stress-early-ifcvt | FileCheck %s
+target triple = "x86_64-apple-macosx10.8.0"
+
+; CHECK: mm2
+define i32 @mm2(i32* nocapture %p, i32 %n) nounwind uwtable readonly ssp {
+entry:
+  br label %do.body
+
+; CHECK: do.body
+; Loop body has no branches before the backedge.
+; CHECK-NOT: LBB
+do.body:
+  %max.0 = phi i32 [ 0, %entry ], [ %max.1, %do.cond ]
+  %min.0 = phi i32 [ 0, %entry ], [ %min.1, %do.cond ]
+  %n.addr.0 = phi i32 [ %n, %entry ], [ %dec, %do.cond ]
+  %p.addr.0 = phi i32* [ %p, %entry ], [ %incdec.ptr, %do.cond ]
+  %incdec.ptr = getelementptr inbounds i32* %p.addr.0, i64 1
+  %0 = load i32* %p.addr.0, align 4
+  %cmp = icmp sgt i32 %0, %max.0
+  br i1 %cmp, label %do.cond, label %if.else
+
+if.else:
+  %cmp1 = icmp slt i32 %0, %min.0
+  %.min.0 = select i1 %cmp1, i32 %0, i32 %min.0
+  br label %do.cond
+
+do.cond:
+  %max.1 = phi i32 [ %0, %do.body ], [ %max.0, %if.else ]
+  %min.1 = phi i32 [ %min.0, %do.body ], [ %.min.0, %if.else ]
+; CHECK: decl %esi
+; CHECK: jne LBB
+  %dec = add i32 %n.addr.0, -1
+  %tobool = icmp eq i32 %dec, 0
+  br i1 %tobool, label %do.end, label %do.body
+
+do.end:
+  %sub = sub nsw i32 %max.1, %min.1
+  ret i32 %sub
+}