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[CIR][CIRGen] Create a new block after break and continue #611

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Jun 6, 2024
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[CIR][CIRGen] Create a new block after break and continue #611

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21 changes: 10 additions & 11 deletions clang/lib/CIR/CodeGen/CIRGenStmt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -551,20 +551,11 @@ mlir::LogicalResult CIRGenFunction::buildGotoStmt(const GotoStmt &S) {
// info support just yet, look at this again once we have it.
assert(builder.getInsertionBlock() && "not yet implemented");

mlir::Block *currBlock = builder.getBlock();
mlir::Block *gotoBlock = currBlock;
if (!currBlock->empty() &&
currBlock->back().hasTrait<mlir::OpTrait::IsTerminator>()) {
gotoBlock = builder.createBlock(builder.getBlock()->getParent());
builder.setInsertionPointToEnd(gotoBlock);
}
Comment on lines -554 to -560
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This part of code was used for test shouldCreateBlkForGoto in clang/test/CIR/CodeGen/goto.cpp. However, it is unrelated to goto, but a workaround for the broken code for break. This patch also moves the test to switch.cpp and renamed it to unreachable_after_break_1.


// A goto marks the end of a block, create a new one for codegen after
// buildGotoStmt can resume building in that block.

builder.create<mlir::cir::GotoOp>(getLoc(S.getSourceRange()),
S.getLabel()->getName());

// A goto marks the end of a block, create a new one for codegen after
// buildGotoStmt can resume building in that block.
// Insert the new block to continue codegen after goto.
builder.createBlock(builder.getBlock()->getParent());

Expand Down Expand Up @@ -597,11 +588,19 @@ mlir::LogicalResult CIRGenFunction::buildLabel(const LabelDecl *D) {
mlir::LogicalResult
CIRGenFunction::buildContinueStmt(const clang::ContinueStmt &S) {
builder.createContinue(getLoc(S.getContinueLoc()));

// Insert the new block to continue codegen after the continue statement.
builder.createBlock(builder.getBlock()->getParent());

return mlir::success();
}

mlir::LogicalResult CIRGenFunction::buildBreakStmt(const clang::BreakStmt &S) {
builder.createBreak(getLoc(S.getBreakLoc()));

// Insert the new block to continue codegen after the break statement.
builder.createBlock(builder.getBlock()->getParent());

return mlir::success();
}

Expand Down
20 changes: 0 additions & 20 deletions clang/test/CIR/CodeGen/goto.cpp
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Expand Up @@ -101,26 +101,6 @@ int shouldGenBranch(int x) {
// NOFLAT: ^bb1:
// NOFLAT: cir.label "err"

int shouldCreateBlkForGoto(int a) {
switch (a) {
case(42):
break;
goto exit;
default:
return 0;
};

exit:
return -1;

}
// NOFLAT: cir.func @_Z22shouldCreateBlkForGotoi
// NOFLAT: case (equal, 42) {
// NOFLAT: cir.break
// NOFLAT: ^bb1: // no predecessors
// NOFLAT: cir.goto "exit"
// NOFLAT: }

void severalLabelsInARow(int a) {
int b = a;
goto end1;
Expand Down
52 changes: 52 additions & 0 deletions clang/test/CIR/CodeGen/loop.cpp
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Expand Up @@ -205,3 +205,55 @@ void l6() {
// CHECK-NEXT: }
// CHECK-NEXT: cir.return
// CHECK-NEXT: }

void unreachable_after_break() {
for (;;) {
break;
int x = 1;
}
}

// CHECK-NEXT: cir.func @_Z23unreachable_after_breakv()
// CHECK-NEXT: cir.scope {
// CHECK-NEXT: %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["x", init] {alignment = 4 : i64}
// CHECK-NEXT: cir.for : cond {
// CHECK-NEXT: %1 = cir.const #true
// CHECK-NEXT: cir.condition(%1)
// CHECK-NEXT: } body {
// CHECK-NEXT: cir.break
// CHECK-NEXT: ^bb1: // no predecessors
// CHECK-NEXT: %1 = cir.const #cir.int<1> : !s32i
// CHECK-NEXT: cir.store %1, %0 : !s32i, !cir.ptr<!s32i>
// CHECK-NEXT: cir.yield
// CHECK-NEXT: } step {
// CHECK-NEXT: cir.yield
// CHECK-NEXT: }
// CHECK-NEXT: }
// CHECK-NEXT: cir.return
// CHECK-NEXT: }

void unreachable_after_continue() {
for (;;) {
continue;
int x = 1;
}
}

// CHECK-NEXT: cir.func @_Z26unreachable_after_continuev()
// CHECK-NEXT: cir.scope {
// CHECK-NEXT: %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["x", init] {alignment = 4 : i64}
// CHECK-NEXT: cir.for : cond {
// CHECK-NEXT: %1 = cir.const #true
// CHECK-NEXT: cir.condition(%1)
// CHECK-NEXT: } body {
// CHECK-NEXT: cir.continue
// CHECK-NEXT: ^bb1: // no predecessors
// CHECK-NEXT: %1 = cir.const #cir.int<1> : !s32i
// CHECK-NEXT: cir.store %1, %0 : !s32i, !cir.ptr<!s32i>
// CHECK-NEXT: cir.yield
// CHECK-NEXT: } step {
// CHECK-NEXT: cir.yield
// CHECK-NEXT: }
// CHECK-NEXT: }
// CHECK-NEXT: cir.return
// CHECK-NEXT: }
19 changes: 19 additions & 0 deletions clang/test/CIR/CodeGen/return.cpp
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Expand Up @@ -12,3 +12,22 @@ int &ret0(int &x) {
// CHECK: cir.store %2, %1 : !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>
// CHECK: %3 = cir.load %1 : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
// CHECK: cir.return %3 : !cir.ptr<!s32i>

int unreachable_after_return() {
return 0;
return 1;
}

// CHECK: cir.func @_Z24unreachable_after_returnv
// CHECK-NEXT: %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["__retval"] {alignment = 4 : i64}
// CHECK-NEXT: %1 = cir.const #cir.int<0> : !s32i
// CHECK-NEXT: cir.store %1, %0 : !s32i, !cir.ptr<!s32i>
// CHECK-NEXT: cir.br ^bb1
// CHECK-NEXT: ^bb1: // 2 preds: ^bb0, ^bb2
// CHECK-NEXT: %2 = cir.load %0 : !cir.ptr<!s32i>, !s32i
// CHECK-NEXT: cir.return %2 : !s32i
// CHECK-NEXT: ^bb2: // no predecessors
// CHECK-NEXT: %3 = cir.const #cir.int<1> : !s32i
// CHECK-NEXT: cir.store %3, %0 : !s32i, !cir.ptr<!s32i>
// CHECK-NEXT: cir.br ^bb1
// CHECK-NEXT: }
22 changes: 22 additions & 0 deletions clang/test/CIR/CodeGen/switch-unreachable-after-break.cpp
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@@ -0,0 +1,22 @@
// RUN: %clang_cc1 -std=c++17 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
// RUN: FileCheck --input-file=%t.cir %s
// XFAIL: *
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These tests are failing because the insertion point is restored by an InsertionGuard in buildSwitchBody(). I suggest revising that part after #528 is merged to avoid conflict.

clangir/clang/lib/CIR/CodeGen/CIRGenStmt.cpp

Lines 972 to 978 in 3da10fa

} else if (lastCaseBlock) {
// This means it's a random stmt following up a case, just
// emit it as part of previous known case.
mlir::OpBuilder::InsertionGuard guardCase(builder);
builder.setInsertionPointToEnd(lastCaseBlock);
res = buildStmt(c, /*useCurrentScope=*/!isa<CompoundStmt>(c));
} else {


void unreachable_after_break(int a) {
switch(a) {
case 0:
break;
break;
int x = 1;
}
}

int unreachable_after_return(int a) {
switch (a) {
case 0:
return 0;
return 1;
int x = 1;
}
return 2;
}
20 changes: 20 additions & 0 deletions clang/test/CIR/CodeGen/switch.cpp
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Expand Up @@ -327,3 +327,23 @@ void fallthrough(int x) {
// CHECK-NEXT: }
// CHECK-NEXT: ]
// CHECK-NEXT: }

int unreachable_after_break_1(int a) {
switch (a) {
case(42):
break;
goto exit;
default:
return 0;
};

exit:
return -1;

}
// CHECK: cir.func @_Z25unreachable_after_break_1i
// CHECK: case (equal, 42) {
// CHECK: cir.break
// CHECK: ^bb1: // no predecessors
// CHECK: cir.goto "exit"
// CHECK: }
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