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llvm-mirror/test/CodeGen/X86/switch-jump-table.ll
Cong Hou 5d51a489ae Replace all weight-based interfaces in MBB with probability-based interfaces, and update all uses of old interfaces.
(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
2015-12-01 05:29:22 +00:00

93 lines
2.1 KiB
LLVM

; RUN: llc -mtriple=i686-pc-gnu-linux < %s | FileCheck %s -check-prefix=CHECK
; RUN: llc -mtriple=i686-pc-gnu-linux -print-machineinstrs=expand-isel-pseudos %s -o /dev/null 2>&1 | FileCheck %s -check-prefix=CHECK-JT-PROB
; An unreachable default destination is replaced with the most popular case label.
define void @foo(i32 %x, i32* %to) {
; CHECK-LABEL: foo:
; CHECK: movl 4(%esp), [[REG:%e[a-z]{2}]]
; CHECK: cmpl $3, [[REG]]
; CHECK: ja .LBB0_6
; CHECK-NEXT: # BB#1:
; CHECK-NEXT: jmpl *.LJTI0_0(,[[REG]],4)
; CHECK: movl $4
; CHECK: retl
entry:
switch i32 %x, label %default [
i32 0, label %bb0
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
i32 5, label %bb4
]
bb0:
store i32 0, i32* %to
br label %exit
bb1:
store i32 1, i32* %to
br label %exit
bb2:
store i32 2, i32* %to
br label %exit
bb3:
store i32 3, i32* %to
br label %exit
bb4:
store i32 4, i32* %to
br label %exit
exit:
ret void
default:
unreachable
; The jump table has four entries.
; CHECK-LABEL: .LJTI0_0:
; CHECK-NEXT: .long .LBB0_2
; CHECK-NEXT: .long .LBB0_3
; CHECK-NEXT: .long .LBB0_4
; CHECK-NEXT: .long .LBB0_5
}
; Check if branch probabilities are correctly assigned to the jump table.
define void @bar(i32 %x, i32* %to) {
; CHECK-JT-PROB-LABEL: bar:
; CHECK-JT-PROB: Successors according to CFG: BB#6({{[0-9a-fx/= ]+}}14.29%) BB#8({{[0-9a-fx/= ]+}}85.71%)
; CHECK-JT-PROB: Successors according to CFG: BB#1({{[0-9a-fx/= ]+}}16.67%) BB#2({{[0-9a-fx/= ]+}}16.67%) BB#3({{[0-9a-fx/= ]+}}16.67%) BB#4({{[0-9a-fx/= ]+}}16.67%) BB#5({{[0-9a-fx/= ]+}}33.33%)
entry:
switch i32 %x, label %default [
i32 0, label %bb0
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
i32 5, label %bb4
], !prof !1
bb0:
store i32 0, i32* %to
br label %exit
bb1:
store i32 1, i32* %to
br label %exit
bb2:
store i32 2, i32* %to
br label %exit
bb3:
store i32 3, i32* %to
br label %exit
bb4:
store i32 4, i32* %to
br label %exit
default:
store i32 5, i32* %to
br label %exit
exit:
ret void
}
!1 = !{!"branch_weights", i32 16, i32 16, i32 16, i32 16, i32 16, i32 16, i32 16}