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Revert "NewGVN: Make unreachable blocks be marked with unreachable"

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This reverts commit r293196

Besides making things look nicer, ATM, we'd like to preserve analysis
more than we'd like to destroy the CFG.  We'll probably revisit in the future

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293501 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Daniel Berlin
2017-01-30 17:06:55 +00:00
parent 549b31f040
commit 77a24c81b1
3 changed files with 38 additions and 33 deletions
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lib/Transforms/Scalar/NewGVN.cpp
+18 -13
View File
@@ -2106,21 +2106,26 @@ void NewGVN::deleteInstructionsInBlock(BasicBlock *BB) {
DEBUG(dbgs() << " BasicBlock Dead:" << *BB);
++NumGVNBlocksDeleted;
// Change to unreachable does not handle destroying phi nodes. We just replace
// the users with undef.
if (BB->empty())
// Check to see if there are non-terminating instructions to delete.
if (isa<TerminatorInst>(BB->begin()))
return;
auto BBI = BB->begin();
while (auto *Phi = dyn_cast<PHINode>(BBI)) {
Phi->replaceAllUsesWith(UndefValue::get(Phi->getType()));
++BBI;
}
Instruction *ToKill = &*BBI;
// Nothing but phi nodes, so nothing left to remove.
if (!ToKill)
return;
NumGVNInstrDeleted += changeToUnreachable(ToKill, false);
// Delete the instructions backwards, as it has a reduced likelihood of having
// to update as many def-use and use-def chains. Start after the terminator.
auto StartPoint = BB->rbegin();
++StartPoint;
// Note that we explicitly recalculate BB->rend() on each iteration,
// as it may change when we remove the first instruction.
for (BasicBlock::reverse_iterator I(StartPoint); I != BB->rend();) {
Instruction &Inst = *I++;
if (!Inst.use_empty())
Inst.replaceAllUsesWith(UndefValue::get(Inst.getType()));
if (isa<LandingPadInst>(Inst))
continue;
Inst.eraseFromParent();
++NumGVNInstrDeleted;
}
}
void NewGVN::markInstructionForDeletion(Instruction *I) {
test/Transforms/NewGVN/2008-12-09-SelfRemove.ll
+19 -19
View File
@@ -1,4 +1,3 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -newgvn -S | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
@@ -10,29 +9,30 @@ target triple = "i386-apple-darwin9.5"
%struct.demangle_component = type { i32, { %struct.anon } }
define void @d_print_mod_list(%struct.d_print_info* %dpi, %struct.d_print_mod* %mods, i32 %suffix) nounwind {
; CHECK-LABEL: @d_print_mod_list(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr [[STRUCT_D_PRINT_INFO:%.*]], %struct.d_print_info* [[DPI:%.*]], i32 0, i32 1
; CHECK-NEXT: br i1 false, label [[RETURN:%.*]], label [[BB:%.*]]
; CHECK: bb:
; CHECK-NEXT: br label [[BB21:%.*]]
; CHECK: bb21:
; CHECK-NEXT: br label [[BB21]]
; CHECK: return:
; CHECK-NEXT: unreachable
;
entry:
%0 = getelementptr %struct.d_print_info, %struct.d_print_info* %dpi, i32 0, i32 1 ; <i8**> [#uses=1]
br i1 false, label %return, label %bb
%0 = getelementptr %struct.d_print_info, %struct.d_print_info* %dpi, i32 0, i32 1 ; <i8**> [#uses=1]
br i1 false, label %return, label %bb
bb: ; preds = %entry
%1 = load i8*, i8** %0, align 4 ; <i8*> [#uses=0]
%2 = getelementptr %struct.d_print_info, %struct.d_print_info* %dpi, i32 0, i32 1 ; <i8**> [#uses=0]
br label %bb21
%1 = load i8*, i8** %0, align 4 ; <i8*> [#uses=0]
%2 = getelementptr %struct.d_print_info, %struct.d_print_info* %dpi, i32 0, i32 1 ; <i8**> [#uses=0]
br label %bb21
bb21: ; preds = %bb21, %bb
br label %bb21
br label %bb21
return: ; preds = %entry
ret void
ret void
}
; CHECK: define void @d_print_mod_list(%struct.d_print_info* %dpi, %struct.d_print_mod* %mods, i32 %suffix) #0 {
; CHECK: entry:
; CHECK: %0 = getelementptr %struct.d_print_info, %struct.d_print_info* %dpi, i32 0, i32 1
; CHECK: br i1 false, label %return, label %bb
; CHECK: bb:
; CHECK: br label %bb21
; CHECK: bb21:
; CHECK: br label %bb21
; CHECK: return:
; CHECK: ret void
; CHECK: }
test/Transforms/NewGVN/pr31594.ll
+1 -1
View File
@@ -77,7 +77,7 @@ define void @foo(i8* %arg) {
; CHECK-NEXT: i8 6, label [[BB8:%.*]]
; CHECK-NEXT: ]
; CHECK: bb8:
; CHECK-NEXT: unreachable
; CHECK-NEXT: br label [[BB4]]
; CHECK: bb9:
; CHECK-NEXT: store i8 0, i8* [[ARG]], !g !0
; CHECK-NEXT: unreachable