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llvm-project/llvm/test/CodeGen/X86/switch-jump-table.ll

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Assign weights to edges to jump table / bit test header when lowering switch statement. Currently, when lowering switch statement and a new basic block is built for jump table / bit test header, the edge to this new block is not assigned with a correct weight. This patch collects the edge weight from all its successors and assign this sum of weights to the edge (and also the other fall-through edge). Test cases are adjusted accordingly. Differential Revision: http://reviews.llvm.org/D12166#fae6eca7 llvm-svn: 246104
2015-08-27 07:15:32 +08:00
; RUN: llc -mtriple=i686-pc-gnu-linux < %s | FileCheck %s -check-prefix=CHECK
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 13:29:22 +08:00
; 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
SelectionDAG switch lowering: Replace unreachable default with most popular case. This can significantly reduce the size of the switch, allowing for more efficient lowering. I also worked with the idea of exploiting unreachable defaults by omitting the range check for jump tables, but always ended up with a non-neglible binary size increase. It might be worth looking into some more. SimplifyCFG currently does this transformation, but I'm working towards changing that so we can optimize harder based on unreachable defaults. Differential Revision: http://reviews.llvm.org/D6510 llvm-svn: 223566
2014-12-06 09:28:50 +08:00
; An unreachable default destination is replaced with the most popular case label.
Assign weights to edges to jump table / bit test header when lowering switch statement. Currently, when lowering switch statement and a new basic block is built for jump table / bit test header, the edge to this new block is not assigned with a correct weight. This patch collects the edge weight from all its successors and assign this sum of weights to the edge (and also the other fall-through edge). Test cases are adjusted accordingly. Differential Revision: http://reviews.llvm.org/D12166#fae6eca7 llvm-svn: 246104
2015-08-27 07:15:32 +08:00
define void @foo(i32 %x, i32* %to) {
; CHECK-LABEL: foo:
SelectionDAG switch lowering: Replace unreachable default with most popular case. This can significantly reduce the size of the switch, allowing for more efficient lowering. I also worked with the idea of exploiting unreachable defaults by omitting the range check for jump tables, but always ended up with a non-neglible binary size increase. It might be worth looking into some more. SimplifyCFG currently does this transformation, but I'm working towards changing that so we can optimize harder based on unreachable defaults. Differential Revision: http://reviews.llvm.org/D6510 llvm-svn: 223566
2014-12-06 09:28:50 +08:00
; CHECK: movl 4(%esp), [[REG:%e[a-z]{2}]]
SelectionDAG switch lowering: use 'unsigned' to count destination popularity SwitchInst::getNumCases() returns unsinged, so using uint64_t to count cases seems unnecessary. Also fix a missing CHECK in the test case. llvm-svn: 224393
2014-12-17 07:41:59 +08:00
; CHECK: cmpl $3, [[REG]]
Assign weights to edges to jump table / bit test header when lowering switch statement. Currently, when lowering switch statement and a new basic block is built for jump table / bit test header, the edge to this new block is not assigned with a correct weight. This patch collects the edge weight from all its successors and assign this sum of weights to the edge (and also the other fall-through edge). Test cases are adjusted accordingly. Differential Revision: http://reviews.llvm.org/D12166#fae6eca7 llvm-svn: 246104
2015-08-27 07:15:32 +08:00
; CHECK: ja .LBB0_6
; CHECK-NEXT: # BB#1:
; CHECK-NEXT: jmpl *.LJTI0_0(,[[REG]],4)
SelectionDAG switch lowering: Replace unreachable default with most popular case. This can significantly reduce the size of the switch, allowing for more efficient lowering. I also worked with the idea of exploiting unreachable defaults by omitting the range check for jump tables, but always ended up with a non-neglible binary size increase. It might be worth looking into some more. SimplifyCFG currently does this transformation, but I'm working towards changing that so we can optimize harder based on unreachable defaults. Differential Revision: http://reviews.llvm.org/D6510 llvm-svn: 223566
2014-12-06 09:28:50 +08:00
; 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
}
Assign weights to edges to jump table / bit test header when lowering switch statement. Currently, when lowering switch statement and a new basic block is built for jump table / bit test header, the edge to this new block is not assigned with a correct weight. This patch collects the edge weight from all its successors and assign this sum of weights to the edge (and also the other fall-through edge). Test cases are adjusted accordingly. Differential Revision: http://reviews.llvm.org/D12166#fae6eca7 llvm-svn: 246104
2015-08-27 07:15:32 +08:00
; Check if branch probabilities are correctly assigned to the jump table.
define void @bar(i32 %x, i32* %to) {
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 13:29:22 +08:00
; 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%)
Assign weights to edges to jump table / bit test header when lowering switch statement. Currently, when lowering switch statement and a new basic block is built for jump table / bit test header, the edge to this new block is not assigned with a correct weight. This patch collects the edge weight from all its successors and assign this sum of weights to the edge (and also the other fall-through edge). Test cases are adjusted accordingly. Differential Revision: http://reviews.llvm.org/D12166#fae6eca7 llvm-svn: 246104
2015-08-27 07:15:32 +08:00
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}