From 2901243fda3fa68f55f52700d473642e719aa219 Mon Sep 17 00:00:00 2001 From: Chandler Carruth Date: Sun, 20 Nov 2011 09:30:40 +0000 Subject: [PATCH] Add some comments to the latest test case I added here to document what is actually being tested. Also add some FileCheck goodness to much more carefully ensure that the result is the desired result. Before this test would only have failed through an assert failure if the underlying fix were reverted. Also, add some weight metadata and a comment explaining exactly what is going on to a trick section of the test case. Originally, we were getting very unlucky and trying to form a block chain that isn't actually profitable. I'm working on a fix to avoid forming these unprofitable chains, and that would also have masked any failure from this test case. The easy solution is to add some metadata that makes it *really* profitable to form the bad chain here. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145006 91177308-0d34-0410-b5e6-96231b3b80d8 --- test/CodeGen/X86/block-placement.ll | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/test/CodeGen/X86/block-placement.ll b/test/CodeGen/X86/block-placement.ll index 859a7027323..16e98edcd1c 100644 --- a/test/CodeGen/X86/block-placement.ll +++ b/test/CodeGen/X86/block-placement.ll @@ -395,8 +395,27 @@ exit: } define void @fpcmp_unanalyzable_branch(i1 %cond) { +; This function's CFG contains an unanalyzable branch that is likely to be +; split due to having a different high-probability predecessor. +; CHECK: fpcmp_unanalyzable_branch +; CHECK: %entry +; CHECK: %exit +; CHECK-NOT: %if.then +; CHECK-NOT: %if.end +; CHECK-NOT: jne +; CHECK-NOT: jnp +; CHECK: jne +; CHECK-NEXT: jnp +; CHECK-NEXT: %if.then + entry: - br i1 %cond, label %entry.if.then_crit_edge, label %lor.lhs.false +; Note that this branch must be strongly biased toward +; 'entry.if.then_crit_edge' to ensure that we would try to form a chain for +; 'entry' -> 'entry.if.then_crit_edge' -> 'if.then'. It is the last edge in that +; chain which would violate the unanalyzable branch in 'exit', but we won't even +; try this trick unless 'if.then' is believed to almost always be reached from +; 'entry.if.then_crit_edge'. + br i1 %cond, label %entry.if.then_crit_edge, label %lor.lhs.false, !prof !1 entry.if.then_crit_edge: %.pre14 = load i8* undef, align 1, !tbaa !0 @@ -418,3 +437,5 @@ if.then: if.end: ret void } + +!1 = metadata !{metadata !"branch_weights", i32 1000, i32 1} -- 2.34.1