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Backout must-exit based parts of 3fc9882e, and 412eb0 

Not sure these are correct.  I think I missed a case when porting this from the original SCEV change to the IndVar changes.  I may end up reapplying this later with a comment about how this is correct, but in case the current bad feeling turns out to be true, I'm removing from tree while investigating further.
This commit is contained in:
Philip Reames 2021-11-03 15:13:31 -07:00
parent f9e6be5cc1
commit d4708fa480
2 changed files with 45 additions and 57 deletions
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37
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
View File

@ -1461,27 +1461,6 @@ bool IndVarSimplify::canonicalizeExitCondition(Loop *L) {
// have not changed exit counts, or the values produced by the compare.
continue;
}
// If we have a loop which would be undefined if infinite, and it has at
// most one possible dynamic exit, then we can conclude that exit must
// be taken. If that exit must be taken, and we know the LHS can only
// take values in the positive domain, then we can conclude RHS must
// also be in that same range, and replace a signed compare with an
// unsigned one.
// If the exit might not be taken in a well defined program.
if (ExitingBlocks.size() == 1 && SE->loopHasNoAbnormalExits(L) &&
SE->loopIsFiniteByAssumption(L)) {
// We have now matched icmp signed-cond zext(X), zext(Y'), and can thus
// replace the signed condition with the unsigned version.
ICmp->setPredicate(ICmp->getUnsignedPredicate());
Changed = true;
// Given we've changed exit counts, notify SCEV.
// Some nested loops may share same folded exit basic block,
// thus we need to notify top most loop.
SE->forgetTopmostLoop(L);
continue;
}
}
// Now that we've canonicalized the condition to match the extend,
@ -1542,22 +1521,6 @@ bool IndVarSimplify::canonicalizeExitCondition(Loop *L) {
// previously visible.
continue;
}
// If we have a loop which would be undefined if infinite, and it has at
// most one possible dynamic exit, then we can conclude that exit must
// be taken. If that exit must be taken, and we know the LHS can only
// take values in the positive domain, then we can conclude RHS must
// also be in that same range.
if (ExitingBlocks.size() == 1 && SE->loopHasNoAbnormalExits(L) &&
SE->loopIsFiniteByAssumption(L)) {
doRotateTransform();
Changed = true;
// Given we've changed exit counts, notify SCEV.
// Some nested loops may share same folded exit basic block,
// thus we need to notify top most loop.
SE->forgetTopmostLoop(L);
continue;
}
}
return Changed;

65
llvm/test/Transforms/IndVarSimplify/finite-exit-comparisons.ll
View File

@ -100,14 +100,13 @@ for.end: ; preds = %for.body, %entry
define void @slt_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @slt_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: [[UMAX:%.*]] = call i8 @llvm.umax.i8(i8 [[TMP0]], i8 1)
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8 [[IV_NEXT]], [[UMAX]]
; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
@ -444,12 +443,12 @@ for.end: ; preds = %for.body, %entry
define void @sgt_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @sgt_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[IV_NEXT]], [[TMP0]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@ -498,12 +497,12 @@ for.end: ; preds = %for.body, %entry
define void @sle_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @sle_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ule i8 [[IV_NEXT]], [[TMP0]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp sle i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@ -552,12 +551,12 @@ for.end: ; preds = %for.body, %entry
define void @sge_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @sge_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[IV_NEXT]], [[TMP0]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp sge i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@ -606,14 +605,13 @@ for.end: ; preds = %for.body, %entry
define void @ult_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @ult_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: [[UMAX:%.*]] = call i8 @llvm.umax.i8(i8 [[TMP0]], i8 1)
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ne i8 [[IV_NEXT]], [[UMAX]]
; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
@ -658,15 +656,42 @@ for.end: ; preds = %for.body, %entry
ret void
}
define void @ugt_neg_non_loop(i16 %n.raw, i8 %start) mustprogress {
; CHECK-LABEL: @ugt_neg_non_loop(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ [[START:%.*]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i16 [[ZEXT]], -2
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br label %for.body
for.body: ; preds = %entry, %for.body
%iv = phi i8 [ %iv.next, %for.body ], [ %start, %entry ]
%iv.next = add i8 %iv, 1
%zext = zext i8 %iv.next to i16
%cmp = icmp ugt i16 %zext, -2
br i1 %cmp, label %for.body, label %for.end
for.end: ; preds = %for.body, %entry
ret void
}
define void @ugt_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @ugt_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[IV_NEXT]], [[TMP0]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@ -715,12 +740,12 @@ for.end: ; preds = %for.body, %entry
define void @ule_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @ule_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ule i8 [[IV_NEXT]], [[TMP0]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp ule i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
@ -769,12 +794,12 @@ for.end: ; preds = %for.body, %entry
define void @uge_non_constant_rhs(i16 %n) mustprogress {
; CHECK-LABEL: @uge_non_constant_rhs(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = trunc i16 [[N:%.*]] to i8
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i8 [[IV_NEXT]], [[TMP0]]
; CHECK-NEXT: [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
; CHECK-NEXT: [[CMP:%.*]] = icmp uge i16 [[ZEXT]], [[N:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void