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llvm-project/llvm/test/CodeGen/ARM/indirectbr-3.ll

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Test: Add REQUIRES: asserts to test that now requires stats. Test was modified in r279670 llvm-svn: 279690
2016-08-25 08:06:52 +08:00
; REQUIRES: asserts
IfConversion: Rescan diamonds. The cost of predicating a diamond is only the instructions that are not shared between the two branches. Additionally If a predicate clobbering instruction occurs in the shared portion of the branches (e.g. a cond move), it may still be possible to if convert the sub-cfg. This change handles these two facts by rescanning the non-shared portion of a diamond sub-cfg to recalculate both the predication cost and whether both blocks are pred-clobbering. Fixed 2 bugs before recommitting. Branch instructions must be compared and found identical before diamond conversion. Also, predicate-clobbering instructions in the shared prefix disqualifies a potential diamond conversion. Includes tests for both. llvm-svn: 279670
2016-08-25 05:34:24 +08:00
; RUN: llc < %s -mtriple=thumbv7-apple-ios -arm-atomic-cfg-tidy=0 -stats 2>&1 | FileCheck %s
Refactor AnalyzeBranch on ARM. The previous version did not always analyze indirect branches correctly. Under some circumstances, this led to the deletion of basic blocks that were the destination of indirect branches. In that case it left indirect branches to nowhere in the code. This patch replaces, and is more general than either of the previous fixes for indirect-branch-analysis issues, r181161 and r186461. For other branches (not indirect) this refactor should have *almost* identical behavior to the previous version. There are some corner cases where this refactor is able to analyze blocks that the previous version could not (e.g. this necessitated the update to thumb2-ifcvt2.ll). <rdar://problem/14464830> llvm-svn: 186735
2013-07-20 07:52:47 +08:00
; If ARMBaseInstrInfo::AnalyzeBlocks returns the wrong value, which was possible
; for blocks with indirect branches, the IfConverter could end up deleting
; blocks that were the destinations of indirect branches, leaving branches to
; nowhere.
; <rdar://problem/14464830>
define i32 @preserve_blocks(i32 %x) {
; preserve_blocks:
; CHECK: Block address taken
[IfConversion] Maintain the CFG when predicating/merging blocks in IfConvert* Summary: This fixes PR32721 in IfConvertTriangle and possible similar problems in IfConvertSimple, IfConvertDiamond and IfConvertForkedDiamond. In PR32721 we had a triangle EBB | \ | | | TBB | / FBB where FBB didn't have any successors at all since it ended with an unconditional return. Then TBB and FBB were be merged into EBB, but EBB would still keep its successors, and the use of analyzeBranch and CorrectExtraCFGEdges wouldn't help to remove them since the return instruction is not analyzable (at least not on ARM). The edge updating code and branch probability updating code is now pushed into MergeBlocks() which allows us to share the same update logic between more callsites. This lets us remove several dependencies on analyzeBranch and completely eliminate RemoveExtraEdges. One thing that showed up with this patch was that IfConversion sometimes left a successor with 0% probability even if there was no branch or fallthrough to the successor. One such example from the test case ifcvt_bad_zero_prob_succ.mir. The indirect branch tBRIND can only jump to bb.1, but without the patch we got: bb.0: successors: %bb.1(0x80000000) bb.1: successors: %bb.1(0x80000000), %bb.2(0x00000000) tBRIND %r1, 1, %cpsr B %bb.1 bb.2: There is no way to jump from bb.1 to bb2, but still there is a 0% edge from bb.1 to bb.2. With the patch applied we instead get the expected: bb.0: successors: %bb.1(0x80000000) bb.1: successors: %bb.1(0x80000000) tBRIND %r1, 1, %cpsr B %bb.1 Since bb.2 had no predecessor at all, it was removed. Several testcases had to be updated due to this since the removed successor made the "Branch Probability Basic Block Placement" pass sometimes place blocks in a different order. Finally added a couple of new test cases: * PR32721_ifcvt_triangle_unanalyzable.mir: Regression test for the original problem dexcribed in PR 32721. * ifcvt_triangleWoCvtToNextEdge.mir: Regression test for problem that caused a revert of my first attempt to solve PR 32721. * ifcvt_simple_bad_zero_prob_succ.mir: Test case showing the problem where a wrong successor with 0% probability was previously left. * ifcvt_[diamond|forked_diamond|simple]_unanalyzable.mir Very simple test cases for the simple and (forked) diamond cases involving unanalyzable branches that can be nice to have as a base if wanting to write more complicated tests. Reviewers: iteratee, MatzeB, grosser, kparzysz Reviewed By: kparzysz Subscribers: kbarton, davide, aemerson, nemanjai, javed.absar, kristof.beyls, llvm-commits Differential Revision: https://reviews.llvm.org/D34099 llvm-svn: 310697
2017-08-11 14:57:08 +08:00
; CHECK: %ibt1
IfConversion: Rescan diamonds. The cost of predicating a diamond is only the instructions that are not shared between the two branches. Additionally If a predicate clobbering instruction occurs in the shared portion of the branches (e.g. a cond move), it may still be possible to if convert the sub-cfg. This change handles these two facts by rescanning the non-shared portion of a diamond sub-cfg to recalculate both the predication cost and whether both blocks are pred-clobbering. Fixed 2 bugs before recommitting. Branch instructions must be compared and found identical before diamond conversion. Also, predicate-clobbering instructions in the shared prefix disqualifies a potential diamond conversion. Includes tests for both. llvm-svn: 279670
2016-08-25 05:34:24 +08:00
; CHECK: movs r0, #2
[IfConversion] Maintain the CFG when predicating/merging blocks in IfConvert* Summary: This fixes PR32721 in IfConvertTriangle and possible similar problems in IfConvertSimple, IfConvertDiamond and IfConvertForkedDiamond. In PR32721 we had a triangle EBB | \ | | | TBB | / FBB where FBB didn't have any successors at all since it ended with an unconditional return. Then TBB and FBB were be merged into EBB, but EBB would still keep its successors, and the use of analyzeBranch and CorrectExtraCFGEdges wouldn't help to remove them since the return instruction is not analyzable (at least not on ARM). The edge updating code and branch probability updating code is now pushed into MergeBlocks() which allows us to share the same update logic between more callsites. This lets us remove several dependencies on analyzeBranch and completely eliminate RemoveExtraEdges. One thing that showed up with this patch was that IfConversion sometimes left a successor with 0% probability even if there was no branch or fallthrough to the successor. One such example from the test case ifcvt_bad_zero_prob_succ.mir. The indirect branch tBRIND can only jump to bb.1, but without the patch we got: bb.0: successors: %bb.1(0x80000000) bb.1: successors: %bb.1(0x80000000), %bb.2(0x00000000) tBRIND %r1, 1, %cpsr B %bb.1 bb.2: There is no way to jump from bb.1 to bb2, but still there is a 0% edge from bb.1 to bb.2. With the patch applied we instead get the expected: bb.0: successors: %bb.1(0x80000000) bb.1: successors: %bb.1(0x80000000) tBRIND %r1, 1, %cpsr B %bb.1 Since bb.2 had no predecessor at all, it was removed. Several testcases had to be updated due to this since the removed successor made the "Branch Probability Basic Block Placement" pass sometimes place blocks in a different order. Finally added a couple of new test cases: * PR32721_ifcvt_triangle_unanalyzable.mir: Regression test for the original problem dexcribed in PR 32721. * ifcvt_triangleWoCvtToNextEdge.mir: Regression test for problem that caused a revert of my first attempt to solve PR 32721. * ifcvt_simple_bad_zero_prob_succ.mir: Test case showing the problem where a wrong successor with 0% probability was previously left. * ifcvt_[diamond|forked_diamond|simple]_unanalyzable.mir Very simple test cases for the simple and (forked) diamond cases involving unanalyzable branches that can be nice to have as a base if wanting to write more complicated tests. Reviewers: iteratee, MatzeB, grosser, kparzysz Reviewed By: kparzysz Subscribers: kbarton, davide, aemerson, nemanjai, javed.absar, kristof.beyls, llvm-commits Differential Revision: https://reviews.llvm.org/D34099 llvm-svn: 310697
2017-08-11 14:57:08 +08:00
; CHECK: Block address taken
; CHECK: %ibt2
; CHECK: movs r0, #1
Refactor AnalyzeBranch on ARM. The previous version did not always analyze indirect branches correctly. Under some circumstances, this led to the deletion of basic blocks that were the destination of indirect branches. In that case it left indirect branches to nowhere in the code. This patch replaces, and is more general than either of the previous fixes for indirect-branch-analysis issues, r181161 and r186461. For other branches (not indirect) this refactor should have *almost* identical behavior to the previous version. There are some corner cases where this refactor is able to analyze blocks that the previous version could not (e.g. this necessitated the update to thumb2-ifcvt2.ll). <rdar://problem/14464830> llvm-svn: 186735
2013-07-20 07:52:47 +08:00
; CHECK-NOT: Address of block that was removed by CodeGen
IfConversion: Rescan diamonds. The cost of predicating a diamond is only the instructions that are not shared between the two branches. Additionally If a predicate clobbering instruction occurs in the shared portion of the branches (e.g. a cond move), it may still be possible to if convert the sub-cfg. This change handles these two facts by rescanning the non-shared portion of a diamond sub-cfg to recalculate both the predication cost and whether both blocks are pred-clobbering. Fixed 2 bugs before recommitting. Branch instructions must be compared and found identical before diamond conversion. Also, predicate-clobbering instructions in the shared prefix disqualifies a potential diamond conversion. Includes tests for both. llvm-svn: 279670
2016-08-25 05:34:24 +08:00
; Separate bug. There are no valid diamonds to if-convert in this file.
; There was a bug in the if-conversion code that would if-convert a false
; diamond where one side had a return and the other had an indirect branch.
; Make sure no diamond conversions occurred while compiling this file.
; CHECK: Statistics Collected
; CHECK-NOT: 1 ifcvt - Number of diamond if-conversions performed
Refactor AnalyzeBranch on ARM. The previous version did not always analyze indirect branches correctly. Under some circumstances, this led to the deletion of basic blocks that were the destination of indirect branches. In that case it left indirect branches to nowhere in the code. This patch replaces, and is more general than either of the previous fixes for indirect-branch-analysis issues, r181161 and r186461. For other branches (not indirect) this refactor should have *almost* identical behavior to the previous version. There are some corner cases where this refactor is able to analyze blocks that the previous version could not (e.g. this necessitated the update to thumb2-ifcvt2.ll). <rdar://problem/14464830> llvm-svn: 186735
2013-07-20 07:52:47 +08:00
entry:
%c2 = icmp slt i32 %x, 3
%blockaddr = select i1 %c2, i8* blockaddress(@preserve_blocks, %ibt1), i8* blockaddress(@preserve_blocks, %ibt2)
%c1 = icmp eq i32 %x, 0
br i1 %c1, label %pre_ib, label %nextblock
nextblock:
ret i32 3
ibt1:
ret i32 2
ibt2:
ret i32 1
pre_ib:
indirectbr i8* %blockaddr, [ label %ibt1, label %ibt2 ]
}