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llvm-mirror/test/Transforms/CodeGenPrepare/skip-merging-case-block.ll
Jun Bum Lim 4f195c2484 [CodeGenPrep] Skip merging empty case blocks
This is recommit of r287553 after fixing the invalid loop info after eliminating an empty block and unit test failures in AVR and WebAssembly :

Summary: Merging an empty case block into the header block of switch could cause ISel to add COPY instructions in the header of switch, instead of the case block, if the case block is used as an incoming block of a PHI. This could potentially increase dynamic instructions, especially when the switch is in a loop. I added a test case which was reduced from the benchmark I was targetting.

Reviewers: t.p.northover, mcrosier, manmanren, wmi, joerg, davidxl

Subscribers: joerg, qcolombet, danielcdh, hfinkel, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D22696

llvm-svn: 289988
2016-12-16 20:38:39 +00:00

201 lines
7.4 KiB
LLVM

; RUN: opt -codegenprepare < %s -mtriple=aarch64-none-linux-gnu -S | FileCheck %s
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64--linux-gnu"
; Expect to skip merging two empty blocks (sw.bb and sw.bb2) into sw.epilog
; as both of them are unlikely executed.
define i32 @f_switch(i32 %c) {
; CHECK-LABEL: @f_switch
; CHECK-LABEL: entry:
; CHECK: i32 10, label %sw.bb
; CHECK: i32 20, label %sw.bb2
entry:
switch i32 %c, label %sw.default [
i32 10, label %sw.bb
i32 20, label %sw.bb2
i32 30, label %sw.bb3
i32 40, label %sw.bb4
], !prof !0
sw.bb: ; preds = %entry
br label %sw.epilog
sw.bb2: ; preds = %entry
br label %sw.epilog
sw.bb3: ; preds = %entry
call void bitcast (void (...)* @callcase3 to void ()*)()
br label %sw.epilog
sw.bb4: ; preds = %entry
call void bitcast (void (...)* @callcase4 to void ()*)()
br label %sw.epilog
sw.default: ; preds = %entry
call void bitcast (void (...)* @calldefault to void ()*)()
br label %sw.epilog
; CHECK-LABEL: sw.epilog:
; CHECK: %fp.0 = phi void (...)* [ @FD, %sw.default ], [ @F4, %sw.bb4 ], [ @F3, %sw.bb3 ], [ @F2, %sw.bb2 ], [ @F1, %sw.bb ]
sw.epilog: ; preds = %sw.default, %sw.bb3, %sw.bb2, %sw.bb
%fp.0 = phi void (...)* [ @FD, %sw.default ], [ @F4, %sw.bb4 ], [ @F3, %sw.bb3 ], [ @F2, %sw.bb2 ], [ @F1, %sw.bb ]
%callee.knr.cast = bitcast void (...)* %fp.0 to void ()*
call void %callee.knr.cast()
ret i32 0
}
; Expect not to merge sw.bb2 because of the conflict in the incoming value from
; sw.bb which is already merged.
define i32 @f_switch2(i32 %c) {
; CHECK-LABEL: @f_switch2
; CHECK-LABEL: entry:
; CHECK: i32 10, label %sw.epilog
; CHECK: i32 20, label %sw.bb2
entry:
switch i32 %c, label %sw.default [
i32 10, label %sw.bb
i32 20, label %sw.bb2
i32 30, label %sw.bb3
i32 40, label %sw.bb4
], !prof !1
sw.bb: ; preds = %entry
br label %sw.epilog
sw.bb2: ; preds = %entry
br label %sw.epilog
sw.bb3: ; preds = %entry
call void bitcast (void (...)* @callcase3 to void ()*)()
br label %sw.epilog
sw.bb4: ; preds = %entry
call void bitcast (void (...)* @callcase4 to void ()*)()
br label %sw.epilog
sw.default: ; preds = %entry
call void bitcast (void (...)* @calldefault to void ()*)()
br label %sw.epilog
; CHECK-LABEL: sw.epilog:
; CHECK: %fp.0 = phi void (...)* [ @FD, %sw.default ], [ @F4, %sw.bb4 ], [ @F3, %sw.bb3 ], [ @F2, %sw.bb2 ], [ @F1, %entry ]
sw.epilog: ; preds = %sw.default, %sw.bb3, %sw.bb2, %sw.bb
%fp.0 = phi void (...)* [ @FD, %sw.default ], [ @F4, %sw.bb4 ], [ @F3, %sw.bb3 ], [ @F2, %sw.bb2 ], [ @F1, %sw.bb ]
%callee.knr.cast = bitcast void (...)* %fp.0 to void ()*
call void %callee.knr.cast()
ret i32 0
}
; Multiple empty blocks should be considered together if all incoming values
; from them are same. We expect to merge both empty blocks (sw.bb and sw.bb2)
; because the sum of frequencies are higer than the threshold.
define i32 @f_switch3(i32 %c) {
; CHECK-LABEL: @f_switch3
; CHECK-LABEL: entry:
; CHECK: i32 10, label %sw.epilog
; CHECK: i32 20, label %sw.epilog
entry:
switch i32 %c, label %sw.default [
i32 10, label %sw.bb
i32 20, label %sw.bb2
i32 30, label %sw.bb3
i32 40, label %sw.bb4
], !prof !2
sw.bb: ; preds = %entry
br label %sw.epilog
sw.bb2: ; preds = %entry
br label %sw.epilog
sw.bb3: ; preds = %entry
call void bitcast (void (...)* @callcase3 to void ()*)()
br label %sw.epilog
sw.bb4: ; preds = %entry
call void bitcast (void (...)* @callcase4 to void ()*)()
br label %sw.epilog
sw.default: ; preds = %entry
call void bitcast (void (...)* @calldefault to void ()*)()
br label %sw.epilog
; CHECK-LABEL: sw.epilog:
; CHECK: %fp.0 = phi void (...)* [ @FD, %sw.default ], [ @F4, %sw.bb4 ], [ @F3, %sw.bb3 ], [ @F1, %entry ], [ @F1, %entry ]
sw.epilog: ; preds = %sw.default, %sw.bb3, %sw.bb2, %sw.bb
%fp.0 = phi void (...)* [ @FD, %sw.default ], [ @F4, %sw.bb4 ], [ @F3, %sw.bb3 ], [ @F1, %sw.bb2 ], [ @F1, %sw.bb ]
%callee.knr.cast = bitcast void (...)* %fp.0 to void ()*
call void %callee.knr.cast()
ret i32 0
}
declare void @F1(...) local_unnamed_addr
declare void @F2(...) local_unnamed_addr
declare void @F3(...) local_unnamed_addr
declare void @F4(...) local_unnamed_addr
declare void @FD(...) local_unnamed_addr
declare void @callcase3(...) local_unnamed_addr
declare void @callcase4(...) local_unnamed_addr
declare void @calldefault(...) local_unnamed_addr
!0 = !{!"branch_weights", i32 5, i32 1, i32 1,i32 5, i32 5}
!1 = !{!"branch_weights", i32 1 , i32 5, i32 1,i32 1, i32 1}
!2 = !{!"branch_weights", i32 1 , i32 4, i32 1,i32 1, i32 1}
; This test that BFI/BPI is created without any assertion in isMergingEmptyBlockProfitable()
; in the case where empty blocks are removed before creating BFI/BPI.
@b = common global i32 0, align 4
@a = common global i32* null, align 8
define i32 @should_not_assert(i32 %i) local_unnamed_addr {
entry:
%0 = load i32, i32* @b, align 4
%cond = icmp eq i32 %0, 6
br i1 %cond, label %while.cond.preheader, label %sw.epilog
while.cond.preheader: ; preds = %entry
%1 = load i32*, i32** @a, align 8
%magicptr = ptrtoint i32* %1 to i64
%arrayidx = getelementptr inbounds i32, i32* %1, i64 1
br label %while.cond
while.cond: ; preds = %while.cond.preheader, %land.rhs
switch i64 %magicptr, label %land.rhs [
i64 32, label %while.cond2.loopexit
i64 0, label %while.cond2.loopexit
]
land.rhs: ; preds = %while.cond
%2 = load i32, i32* %arrayidx, align 4
%tobool1 = icmp eq i32 %2, 0
br i1 %tobool1, label %while.cond2thread-pre-split.loopexit, label %while.cond
while.cond2thread-pre-split.loopexit: ; preds = %land.rhs
br label %while.cond2thread-pre-split
while.cond2thread-pre-split: ; preds = %while.cond2thread-pre-split.loopexit, %while.body4
%.pr = phi i32* [ %.pr.pre, %while.body4 ], [ %1, %while.cond2thread-pre-split.loopexit ]
br label %while.cond2
while.cond2.loopexit: ; preds = %while.cond, %while.cond
br label %while.cond2
while.cond2: ; preds = %while.cond2.loopexit, %while.cond2thread-pre-split
%3 = phi i32* [ %.pr, %while.cond2thread-pre-split ], [ %1, %while.cond2.loopexit ]
%tobool3 = icmp eq i32* %3, null
br i1 %tobool3, label %sw.epilog, label %while.body4
while.body4: ; preds = %while.cond2
tail call void bitcast (void (...)* @fn2 to void ()*)()
%.pr.pre = load i32*, i32** @a, align 8
br label %while.cond2thread-pre-split
sw.epilog: ; preds = %while.cond2, %entry
ret i32 undef
}
declare void @fn2(...) local_unnamed_addr