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

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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%

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228895 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2015-02-12 01:02:52 +00:00
parent 6f4e8d27e9
commit 091acf253b
2 changed files with 39 additions and 1 deletions
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4
lib/Target/PowerPC/PPCISelLowering.cpp
View File

@ -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())

36
test/CodeGen/PowerPC/no-pref-jumps.ll Normal file
View File

@ -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 }