[PowerPC] Mark jumps as expensive (using using CR bits)

On PowerPC, which has a full set of logical operations on (its multiple sets
of) condition-register bits, it is not profitable to break of complex
conditions feeding a jump into multiple jumps. We can turn off this feature of
CGP/SDAGBuilder by marking jumps as "expensive".

P7 test-suite speedups (no regressions):
MultiSource/Benchmarks/FreeBench/pcompress2/pcompress2
	-0.626647% +/- 0.323583%
MultiSource/Benchmarks/Olden/power/power
	-18.2821% +/- 8.06481%

llvm-svn: 228895

2 files changed, 39 insertions, 1 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 7ecfac66b49..15a0818c816 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -687,8 +687,10 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
 
   // With 32 condition bits, we don't need to sink (and duplicate) compares
   // aggressively in CodeGenPrep.
-  if (Subtarget.useCRBits())
+  if (Subtarget.useCRBits()) {
     setHasMultipleConditionRegisters();
+    setJumpIsExpensive();
+  }
 
   setMinFunctionAlignment(2);
   if (Subtarget.isDarwin())
diff --git a/llvm/test/CodeGen/PowerPC/no-pref-jumps.ll b/llvm/test/CodeGen/PowerPC/no-pref-jumps.ll
new file mode 100644
index 00000000000..d9490f16e8f
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/no-pref-jumps.ll
@@ -0,0 +1,36 @@
+; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+; Function Attrs: nounwind
+define void @foo(i32 signext %a, i32 signext %b) #0 {
+entry:
+  %cmp = icmp sgt i32 %a, 5
+  %cmp1 = icmp slt i32 %b, 3
+  %or.cond = or i1 %cmp, %cmp1
+  br i1 %or.cond, label %if.then, label %if.else
+
+; CHECK-LABEL: @foo
+; CHECK: cmpwi
+; CHECK: cmpwi
+; CHECK: cror
+; CHECK: blr
+
+if.then:                                          ; preds = %entry
+  tail call void bitcast (void (...)* @bar to void ()*)() #0
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  tail call void bitcast (void (...)* @car to void ()*)() #0
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  ret void
+}
+
+declare void @bar(...)
+
+declare void @car(...)
+
+attributes #0 = { nounwind }
+