From e14fb073574dcb74de05bdeedbfb3fcffbfa1bf6 Mon Sep 17 00:00:00 2001 From: Hal Finkel Date: Fri, 1 Nov 2013 10:58:22 +0000 Subject: Consider (x == -1) unlikely in BranchProbabilityInfo This adds another heuristic to BPI, similar to the existing heuristic that considers (x == 0) unlikely to be true. As suggested in the PACT'98 paper by Deitrich, Cheng, and Hwu, -1 is often used to indicate an invalid index, and equality comparisons with -1 are also unlikely to succeed. Local experimentation supports this hypothesis: This yields a 1-2% speedup in the test-suite sqlite benchmark on the PPC A2 core, with no significant regressions. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193855 91177308-0d34-0410-b5e6-96231b3b80d8 --- test/Analysis/BranchProbabilityInfo/basic.ll | 39 ++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) (limited to 'test') diff --git a/test/Analysis/BranchProbabilityInfo/basic.ll b/test/Analysis/BranchProbabilityInfo/basic.ll index c6e1bde81d..05cb31dca0 100644 --- a/test/Analysis/BranchProbabilityInfo/basic.ll +++ b/test/Analysis/BranchProbabilityInfo/basic.ll @@ -173,3 +173,42 @@ exit: %ret = phi i32 [ %val4, %then ], [ %val3, %else ] ret i32 %ret } + +define i32 @zero1(i32 %i, i32 %a, i32 %b) { +; CHECK: Printing analysis {{.*}} for function 'zero1' +entry: + %cond = icmp eq i32 %i, 0 + br i1 %cond, label %then, label %else +; CHECK: edge entry -> then probability is 12 / 32 +; CHECK: edge entry -> else probability is 20 / 32 + +then: + br label %exit + +else: + br label %exit + +exit: + %result = phi i32 [ %a, %then ], [ %b, %else ] + ret i32 %result +} + +define i32 @zero2(i32 %i, i32 %a, i32 %b) { +; CHECK: Printing analysis {{.*}} for function 'zero2' +entry: + %cond = icmp ne i32 %i, -1 + br i1 %cond, label %then, label %else +; CHECK: edge entry -> then probability is 20 / 32 +; CHECK: edge entry -> else probability is 12 / 32 + +then: + br label %exit + +else: + br label %exit + +exit: + %result = phi i32 [ %a, %then ], [ %b, %else ] + ret i32 %result +} + -- cgit v1.2.3