Revert "[flang] make lowering to scf.while default" (#184592)

Reverts llvm/llvm-project#184234 This is breaking SPEC and other tests. Reproducer: ``` subroutine foo() logical :: l1, l2 do while (l1()) if (l2()) then call bar() endif enddo end ``` The cause is a pass ordering issue between the SCFToControlFlowPass and CfgConversionPass [here](d0f50d5574/flang/lib/Optimizer/Passes/Pipelines.cpp (L239-L240)). I think they need to be run simultaneously somehow because the both SCF and FIR structured operations may contain each other, and none will be happy to get block CFG generated inside their region by the pass lowering the other. Reverting while this is sorted out.
2026-03-04 12:42:08 +01:00 · 2026-03-04 12:42:08 +01:00 · ee8184573f
commit ee8184573f
parent 9c2829f2e1
7 changed files with 76 additions and 61 deletions
--- a/flang/lib/Lower/PFTBuilder.cpp
+++ b/flang/lib/Lower/PFTBuilder.cpp
@ -28,6 +28,10 @@ static llvm::cl::opt<bool> clDisableStructuredFir(
 using namespace Fortran;

 namespace {
+static llvm::cl::opt<bool> lowerDoWhileToSCFWhile(
+    "lower-do-while-to-scf-while", llvm::cl::init(false),
+    llvm::cl::desc("lower structured DO WHILE loops to scf.while"),
+    llvm::cl::Hidden);
 /// Helpers to unveil parser node inside Fortran::parser::Statement<>,
 /// Fortran::parser::UnlabeledStatement, and Fortran::common::Indirection<>
 template <typename A>
@ -1058,6 +1062,12 @@ private:
              if (bounds->Name().thing.symbol->GetType()->IsNumeric(
                      common::TypeCategory::Real))
                eval.isUnstructured = true; // real-valued loop control
+            } else if (std::get_if<parser::ScalarLogicalExpr>(
+                           &loopControl->u)) {
+              // Leave DO WHILE structured when -lower-do-while-to-scf-while is
+              // enabled; branch analysis will mark unstructured cases.
+              if (!lowerDoWhileToSCFWhile)
+                eval.isUnstructured = true; // while loop
            }
          },
          [&](const parser::EndDoStmt &) {
--- a/flang/test/Lower/OpenMP/target.f90
+++ b/flang/test/Lower/OpenMP/target.f90
@ -684,21 +684,12 @@ subroutine target_unstructured
      !CHECK-NO-FPRIV: %[[VAL_8:.*]]:2 = hlfir.declare %[[VAL_6]] {uniq_name = "_QFtarget_unstructuredEi"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
      !CHECK-NO-FPRIV: %[[VAL_9:.*]]:2 = hlfir.declare %[[VAL_7]] {uniq_name = "_QFtarget_unstructuredEj"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)

-      !CHECK: scf.while : () -> () {
-      !CHECK:   %[[I_CUR:.*]] = fir.load %[[VAL_8]]#0 : !fir.ref<i32>
-      !CHECK:   %[[J_CUR:.*]] = fir.load %[[VAL_9]]#0 : !fir.ref<i32>
-      !CHECK:   %[[COND:.*]] = arith.cmpi sle, %[[I_CUR]], %[[J_CUR]] : i32
-      !CHECK:   scf.condition(%[[COND]])
-      !CHECK: } do {
-      !CHECK:   %[[I_BODY:.*]] = fir.load %[[VAL_8]]#0 : !fir.ref<i32>
-      !CHECK:   %[[ONE:.*]] = arith.constant 1 : i32
-      !CHECK:   %[[I_NEXT:.*]] = arith.addi %[[I_BODY]], %[[ONE]] : i32
-      !CHECK:   hlfir.assign %[[I_NEXT]] to %[[VAL_8]]#0 : i32, !fir.ref<i32>
-      !CHECK:   scf.yield
-      !CHECK: }
+      !CHECK: ^bb1:
      do while (i <= j)
+         !CHECK: ^bb2:
         i = i + 1
      end do
+      !CHECK: ^bb3:
      !CHECK: omp.terminator
   !$omp end target
   !CHECK: }
--- a/flang/test/Lower/do-while-to-scf-while.f90
+++ b/flang/test/Lower/do-while-to-scf-while.f90
@ -1,4 +1,4 @@
-! RUN: bbc -emit-hlfir %s -o - | FileCheck %s
+! RUN: bbc -emit-hlfir -lower-do-while-to-scf-while %s -o - | FileCheck %s

 ! CHECK-LABEL: func.func @_QPsimple_do_while()
 ! CHECK: scf.while
--- a/flang/test/Lower/loops.f90
+++ b/flang/test/Lower/loops.f90
@ -147,12 +147,12 @@ end
 ! CHECK-LABEL: print_nothing
 subroutine print_nothing(k1, k2)
  if (k1 > 0) then
-    ! CHECK: scf.while : () -> () {
-    ! CHECK: scf.condition
+    ! CHECK: br [[header:\^bb[0-9]+]]
+    ! CHECK: [[header]]
    do while (k1 > k2)
      print*, k1, k2 ! no output
      k2 = k2 + 1
-      ! CHECK: scf.yield
+      ! CHECK: br [[header]]
    end do
  end if
 end
--- a/flang/test/Lower/mixed_loops.f90
+++ b/flang/test/Lower/mixed_loops.f90
@ -3,6 +3,7 @@
 ! Test while loop inside do loop.
 ! CHECK-LABEL: while_inside_do_loop
 subroutine while_inside_do_loop
+  ! CHECK-DAG: %[[T_REF:.*]] = fir.alloca i32
  ! CHECK-DAG: %[[I_ADDR:.*]] = fir.alloca i32 {bindc_name = "i", uniq_name = "_QFwhile_inside_do_loopEi"}
  ! CHECK-DAG: %[[I:.*]]:2 = hlfir.declare %[[I_ADDR]]
  ! CHECK-DAG: %[[J_ADDR:.*]] = fir.alloca i32 {bindc_name = "j", uniq_name = "_QFwhile_inside_do_loopEj"}
@ -11,40 +12,52 @@ subroutine while_inside_do_loop

  ! CHECK-DAG: %[[C8:.*]] = arith.constant 8 : i32
  ! CHECK-DAG: %[[C13:.*]] = arith.constant 13 : i32
-  ! CHECK-DAG: %[[C1:.*]] = arith.constant 1 : index
-  ! CHECK-DAG: %[[LB:.*]] = fir.convert %[[C8]] : (i32) -> index
-  ! CHECK-DAG: %[[UB:.*]] = fir.convert %[[C13]] : (i32) -> index
-  ! CHECK-DAG: %[[INIT:.*]] = fir.convert %[[LB]] : (index) -> i32
-  ! CHECK: %[[RES:.*]] = fir.do_loop %{{.*}} = %[[LB]] to %[[UB]] step %[[C1]] iter_args(%[[I_IV:.*]] = %[[INIT]]) -> (i32) {
-  ! CHECK:   fir.store %[[I_IV]] to %[[I]]#0 : !fir.ref<i32>
+  ! CHECK-DAG: %[[C1:.*]] = arith.constant 1 : i32
+  ! CHECK: %[[DIFF:.*]] = arith.subi %[[C13]], %[[C8]] : i32
+  ! CHECK: %[[RANGE:.*]] = arith.addi %[[DIFF]], %[[C1]] : i32
+  ! CHECK: %[[HIGH:.*]] = arith.divsi %[[RANGE]], %[[C1]] : i32
+  ! CHECK: fir.store %[[HIGH]] to %[[T_REF]] : !fir.ref<i32>
+  ! CHECK: fir.store %[[C8]] to %[[I]]#0 : !fir.ref<i32>
+
+  ! CHECK: cf.br ^[[HDR1:.*]]
+  ! CHECK: ^[[HDR1]]:  // 2 preds: ^{{.*}}, ^[[EXIT2:.*]]
+  ! CHECK: %[[T:.*]] = fir.load %[[T_REF]] : !fir.ref<i32>
+  ! CHECK: %[[C0:.*]] = arith.constant 0 : i32
+  ! CHECK: %[[COND:.*]] = arith.cmpi sgt, %[[T]], %[[C0]] : i32
+  ! CHECK: cf.cond_br %[[COND]], ^[[BODY1:.*]], ^[[EXIT1:.*]]
  do i=8,13
+    ! CHECK: ^[[BODY1]]:  // pred: ^[[HDR1]]
    ! CHECK: %[[C3:.*]] = arith.constant 3 : i32
    ! CHECK: hlfir.assign %[[C3]] to %[[J]]#0 : i32, !fir.ref<i32>
    j=3

-    ! CHECK: scf.while : () -> () {
+    ! CHECK: cf.br ^[[HDR2:.*]]
+    ! CHECK: ^[[HDR2]]:  // 2 preds: ^[[BODY1]], ^[[BODY2:.*]]
    ! CHECK: %[[JVAL:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
    ! CHECK: %[[IVAL:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
    ! CHECK: %[[COND2:.*]] = arith.cmpi slt, %[[JVAL]], %[[IVAL]] : i32
-    ! CHECK: scf.condition(%[[COND2]])
-    ! CHECK: } do {
+    ! CHECK: cf.cond_br %[[COND2]], ^[[BODY2:.*]], ^[[EXIT2]]
    do while (j .lt. i)
+      ! CHECK: ^[[BODY2]]:  // pred: ^[[HDR2]]
      ! CHECK: %[[C2:.*]] = arith.constant 2 : i32
      ! CHECK: %[[JVAL2:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
      ! CHECK: %[[INC2:.*]] = arith.muli %[[C2]], %[[JVAL2]] : i32
      ! CHECK: hlfir.assign %[[INC2]] to %[[J]]#0 : i32, !fir.ref<i32>
      j=j*2
-    ! CHECK: scf.yield
+    ! CHECK: cf.br ^[[HDR2]]
    end do
-    ! CHECK: }

-  ! CHECK: %[[STEP_I32:.*]] = fir.convert %[[C1]] : (index) -> i32
-  ! CHECK: %[[I_CUR:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
-  ! CHECK: %[[I_NEXT:.*]] = arith.addi %[[I_CUR]], %[[STEP_I32]] overflow<nsw> : i32
-  ! CHECK: fir.result %[[I_NEXT]] : i32
-  ! CHECK: fir.store %[[RES]] to %[[I]]#0 : !fir.ref<i32>
+  ! CHECK: ^[[EXIT2]]: // pred: ^[[HDR2]]
+  ! CHECK: %[[T2:.*]] = fir.load %[[T_REF]] : !fir.ref<i32>
+  ! CHECK: %[[TDEC:.*]] = arith.subi %[[T2]], {{.*}} : i32
+  ! CHECK: fir.store %[[TDEC]] to %[[T_REF]]
+  ! CHECK: %[[I3:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
+  ! CHECK: %[[IINC:.*]] = arith.addi %[[I3]], {{.*}} overflow<nsw> : i32
+  ! CHECK: fir.store %[[IINC]] to %[[I]]#0 : !fir.ref<i32>
+  ! CHECK: cf.br ^[[HDR1]]
  end do

+  ! CHECK: ^[[EXIT1]]:  // pred: ^[[HDR1]]
  ! CHECK: %[[IPRINT:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
  ! CHECK: fir.call @_FortranAioOutputInteger32(%{{.*}}, %[[IPRINT]])
  ! CHECK: %[[JPRINT:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
@ -65,21 +78,19 @@ subroutine do_inside_while_loop
    ! CHECK: hlfir.assign %[[C3]] to %[[J]]#0 : i32, !fir.ref<i32>
    j=3

-    ! CHECK: scf.while : () -> () {
+    ! CHECK: cf.br ^[[HDR1:.*]]
+    ! CHECK: ^[[HDR1]]:  // 2 preds: ^{{.*}}, ^[[BODY1:.*]]
    ! CHECK: %[[JVAL:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
    ! CHECK: %[[UL:.*]] = arith.constant 21 : i32
    ! CHECK: %[[COND:.*]] = arith.cmpi slt, %[[JVAL]], %[[UL]] : i32
-    ! CHECK: scf.condition(%[[COND]])
-    ! CHECK: } do {
+    ! CHECK: cf.cond_br %[[COND]], ^[[BODY1]], ^[[EXIT1:.*]]
    do while (j .lt. 21)
+      ! CHECK: ^[[BODY1]]:  // pred: ^[[HDR1]]

      ! CHECK-DAG: %[[C8:.*]] = arith.constant 8 : i32
      ! CHECK-DAG: %[[C13:.*]] = arith.constant 13 : i32
      ! CHECK-DAG: %[[C1:.*]] = arith.constant 1 : index
-      ! CHECK-DAG: %[[LB:.*]] = fir.convert %[[C8]] : (i32) -> index
-      ! CHECK-DAG: %[[UB:.*]] = fir.convert %[[C13]] : (i32) -> index
-      ! CHECK-DAG: %[[INIT:.*]] = fir.convert %[[LB]] : (index) -> i32
-      ! CHECK: %{{.*}} = fir.do_loop %{{.*}} = %[[LB]] to %[[UB]] step %[[C1]] iter_args(%[[I_IV:.*]] = %[[INIT]]) -> (i32) {
+      ! CHECK: %{{.*}} = fir.do_loop %{{.*}} = {{.*}} to {{.*}} step {{.*}} iter_args(%[[I_IV:.*]] = {{.*}}) -> (i32) {
        ! CHECK: fir.store %[[I_IV]] to %[[I]]#0 : !fir.ref<i32>
        ! CHECK: %[[C2:.*]] = arith.constant 2 : i32
        ! CHECK: %[[J2VAL:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
@ -94,10 +105,10 @@ subroutine do_inside_while_loop
      ! CHECK: fir.store %{{.*}} to %[[I]]#0 : !fir.ref<i32>
      end do

-    ! CHECK: scf.yield
+    ! CHECK: cf.br ^[[HDR1]]
    end do
-  ! CHECK: }

+  ! CHECK: ^[[EXIT1]]:  // pred: ^[[HDR1]]
  ! CHECK: %[[IPRINT:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
  ! CHECK: fir.call @_FortranAioOutputInteger32(%{{.*}}, %[[IPRINT]])
  ! CHECK: %[[JPRINT:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
--- a/flang/test/Lower/pre-fir-tree02.f90
+++ b/flang/test/Lower/pre-fir-tree02.f90
@ -82,15 +82,15 @@ program test_prog
      ! CHECK: CaseStmt
      case default
        ! Note: label-do-loop are canonicalized into do constructs
-        ! CHECK: <<DoConstruct>>
-        ! CHECK: [[DO_HDR:[0-9]+]] NonLabelDoStmt -> [[DO_END:[0-9]+]]: do 22 while(l<=k)
+        ! CHECK: <<DoConstruct!>>
+        ! CHECK: NonLabelDoStmt
        do 22 while(l<=k)
          ! CHECK: IfStmt
          if (p(l)<0.) p(l)=cos(p(l))
-          ! CHECK: [[CALL_ID:[0-9]+]] CallStmt: 22 call incr(l)
+          ! CHECK: CallStmt
 22        call incr(l)
-        ! CHECK: [[DO_END]] EndDoStmt -> [[DO_HDR]]
-       ! CHECK: <<End DoConstruct>>
+        ! CHECK: EndDoStmt
+       ! CHECK: <<End DoConstruct!>>
      ! CHECK: CaseStmt
      case (100:)
    ! CHECK: EndSelectStmt
--- a/flang/test/Lower/while_loop.f90
+++ b/flang/test/Lower/while_loop.f90
@ -11,22 +11,23 @@ subroutine simple_loop
  ! CHECK: hlfir.assign %[[C5]] to %[[I]]#0
  i = 5

-  ! CHECK: scf.while : () -> () {
+  ! CHECK: cf.br ^[[BB1:.*]]
+  ! CHECK: ^[[BB1]]:  // 2 preds: ^{{.*}}, ^[[BB2:.*]]
  ! CHECK: %[[IVAL:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
  ! CHECK: %[[C1:.*]] = arith.constant 1 : i32
  ! CHECK: %[[COND:.*]] = arith.cmpi sgt, %[[IVAL]], %[[C1]] : i32
-  ! CHECK: scf.condition(%[[COND]])
-  ! CHECK: } do {
+  ! CHECK: cf.cond_br %[[COND]], ^[[BB2]], ^[[BB3:.*]]
+  ! CHECK: ^[[BB2]]:  // pred: ^[[BB1]]
  ! CHECK: %[[IVAL2:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
  ! CHECK: %[[C2:.*]] = arith.constant 2 : i32
  ! CHECK: %[[INC:.*]] = arith.subi %[[IVAL2]], %[[C2]] : i32
  ! CHECK: hlfir.assign %[[INC]] to %[[I]]#0 : i32, !fir.ref<i32>
-  ! CHECK: scf.yield
-  ! CHECK: }
+  ! CHECK: cf.br ^[[BB1]]
  do while (i .gt. 1)
    i = i - 2
  end do

+  ! CHECK: ^[[BB3]]:  // pred: ^[[BB1]]
  ! CHECK: %[[IVAL3:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
  ! CHECK: fir.call @_FortranAioOutputInteger32(%{{.*}}, %[[IVAL3]])
  print *, i
@ -45,13 +46,14 @@ subroutine while_inside_while_loop
  ! CHECK: hlfir.assign %[[C13]] to %[[I]]#0
  i = 13

-  ! CHECK: scf.while : () -> () {
+  ! CHECK: cf.br ^[[HDR1:.*]]
+  ! CHECK: ^[[HDR1]]:  // 2 preds: ^{{.*}}, ^[[EXIT2:.*]]
  ! CHECK: %[[IVAL:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
  ! CHECK: %[[C8:.*]] = arith.constant 8 : i32
  ! CHECK: %[[COND:.*]] = arith.cmpi sgt, %[[IVAL]], %[[C8]] : i32
-  ! CHECK: scf.condition(%[[COND]])
-  ! CHECK: } do {
+  ! CHECK: cf.cond_br %[[COND]], ^[[BODY1:.*]], ^[[EXIT1:.*]]
  do while (i .gt. 8)
+    ! CHECK: ^[[BODY1]]:  // pred: ^[[HDR1]]
    ! CHECK: %[[IVAL2:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
    ! CHECK: %[[C5:.*]] = arith.constant 5 : i32
    ! CHECK: %[[INC:.*]] = arith.subi %[[IVAL2]], %[[C5]] : i32
@ -62,26 +64,27 @@ subroutine while_inside_while_loop
    ! CHECK: hlfir.assign %[[C3]] to %[[J]]#0
    j = 3

-    ! CHECK: scf.while : () -> () {
+    ! CHECK: cf.br ^[[HDR2:.*]]
+    ! CHECK: ^[[HDR2]]:  // 2 preds: ^[[BODY1]], ^[[BODY2:.*]]
    ! CHECK: %[[JVAL:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
    ! CHECK: %[[IVAL3:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
    ! CHECK: %[[COND2:.*]] = arith.cmpi slt, %[[JVAL]], %[[IVAL3]] : i32
-    ! CHECK: scf.condition(%[[COND2]])
-    ! CHECK: } do {
+    ! CHECK: cf.cond_br %[[COND2]], ^[[BODY2]], ^[[EXIT2:.*]]
    do while (j .lt. i)
+      ! CHECK: ^[[BODY2]]:  // pred: ^[[HDR2]]
      ! CHECK: %[[C2:.*]] = arith.constant 2 : i32
      ! CHECK: %[[JVAL2:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>
      ! CHECK: %[[INC2:.*]] = arith.muli %[[C2]], %[[JVAL2]] : i32
      ! CHECK: hlfir.assign %[[INC2]] to %[[J]]#0 : i32, !fir.ref<i32>
      j = j * 2
-    ! CHECK: scf.yield
+    ! CHECK: cf.br ^[[HDR2]]
    end do
-    ! CHECK: }

-    ! CHECK: scf.yield
+    ! CHECK: ^[[EXIT2]]: // pred: ^[[HDR2]]
+    ! CHECK: cf.br ^[[HDR1]]
  end do
-  ! CHECK: }

+  ! CHECK: ^[[EXIT1]]:  // pred: ^[[HDR1]]
  ! CHECK: %[[IPRINT:.*]] = fir.load %[[I]]#0 : !fir.ref<i32>
  ! CHECK: fir.call @_FortranAioOutputInteger32(%{{.*}}, %[[IPRINT]])
  ! CHECK: %[[JPRINT:.*]] = fir.load %[[J]]#0 : !fir.ref<i32>