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5d51a489ae
(This is the second attempt to submit this patch. The first caused two assertion failures and was reverted. See https://llvm.org/bugs/show_bug.cgi?id=25687) The patch in http://reviews.llvm.org/D13745 is broken into four parts: 1. New interfaces without functional changes (http://reviews.llvm.org/D13908). 2. Use new interfaces in SelectionDAG, while in other passes treat probabilities as weights (http://reviews.llvm.org/D14361). 3. Use new interfaces in all other passes. 4. Remove old interfaces. This patch is 3+4 above. In this patch, MBB won't provide weight-based interfaces any more, which are totally replaced by probability-based ones. The interface addSuccessor() is redesigned so that the default probability is unknown. We allow unknown probabilities but don't allow using it together with known probabilities in successor list. That is to say, we either have a list of successors with all known probabilities, or all unknown probabilities. In the latter case, we assume each successor has 1/N probability where N is the number of successors. An assertion checks if the user is attempting to add a successor with the disallowed mixed use as stated above. This can help us catch many misuses. All uses of weight-based interfaces are now updated to use probability-based ones. Differential revision: http://reviews.llvm.org/D14973 llvm-svn: 254377
45 lines
1.6 KiB
LLVM
45 lines
1.6 KiB
LLVM
; RUN: llc -mtriple=arm-apple-ios -print-machineinstrs=branch-folder \
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; RUN: %s -o /dev/null 2>&1 | FileCheck %s
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; Branch probability of tailed-merged block:
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;
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; p(L0_L1 -> L2) = p(entry -> L0) * p(L0 -> L2) + p(entry -> L1) * p(L1 -> L2)
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; = 0.2 * 0.6 + 0.8 * 0.3 = 0.36
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; p(L0_L1 -> L3) = p(entry -> L0) * p(L0 -> L3) + p(entry -> L1) * p(L1 -> L3)
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; = 0.2 * 0.4 + 0.8 * 0.7 = 0.64
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; CHECK: # Machine code for function test0:
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; CHECK: Successors according to CFG: BB#{{[0-9]+}}({{[0-9a-fx/= ]+}}20.00%) BB#{{[0-9]+}}({{[0-9a-fx/= ]+}}80.00%)
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; CHECK: BB#{{[0-9]+}}:
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; CHECK: BB#{{[0-9]+}}:
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; CHECK: # End machine code for function test0.
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define i32 @test0(i32 %n, i32 %m, i32* nocapture %a, i32* nocapture %b) {
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entry:
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%cmp = icmp sgt i32 %n, 0
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br i1 %cmp, label %L0, label %L1, !prof !0
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L0: ; preds = %entry
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store i32 12, i32* %a, align 4
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store i32 18, i32* %b, align 4
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%cmp1 = icmp eq i32 %m, 8
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br i1 %cmp1, label %L2, label %L3, !prof !1
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L1: ; preds = %entry
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store i32 14, i32* %a, align 4
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store i32 18, i32* %b, align 4
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%cmp3 = icmp eq i32 %m, 8
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br i1 %cmp3, label %L2, label %L3, !prof !2
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L2: ; preds = %L1, %L0
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br label %L3
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L3: ; preds = %L0, %L1, %L2
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%retval.0 = phi i32 [ 100, %L2 ], [ 6, %L1 ], [ 6, %L0 ]
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ret i32 %retval.0
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}
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!0 = !{!"branch_weights", i32 200, i32 800}
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!1 = !{!"branch_weights", i32 600, i32 400}
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!2 = !{!"branch_weights", i32 300, i32 700}
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