[llvm] 05ed921 - Revert "Reland [SimplifyCFG] Delete the unnecessary range check for small mask operation (#70542)"
Hans Wennborg via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 7 01:53:46 PST 2023
Author: Hans Wennborg
Date: 2023-11-07T10:53:22+01:00
New Revision: 05ed92127cebdd483f1ae2039d8e16917055621d
URL: https://github.com/llvm/llvm-project/commit/05ed92127cebdd483f1ae2039d8e16917055621d
DIFF: https://github.com/llvm/llvm-project/commit/05ed92127cebdd483f1ae2039d8e16917055621d.diff
LOG: Revert "Reland [SimplifyCFG] Delete the unnecessary range check for small mask operation (#70542)"
This caused https://github.com/llvm/llvm-project/issues/71329
> Fix the compile crash when the default result has no result for
> https://github.com/llvm/llvm-project/pull/65835
>
> Fixes https://github.com/llvm/llvm-project/issues/65120
> Reviewed By: zmodem, nikic
This reverts commit 7c4180a36a905b7ed46c09df77af1b65e356f92a.
Added:
Modified:
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/test/Transforms/SimplifyCFG/switch_mask.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index b58bcd35f940f96..5ef3a5292af545c 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6598,8 +6598,9 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
// If the default destination is unreachable, or if the lookup table covers
// all values of the conditional variable, branch directly to the lookup table
// BB. Otherwise, check that the condition is within the case range.
- bool DefaultIsReachable =
+ const bool DefaultIsReachable =
!isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
+ const bool GeneratingCoveredLookupTable = (MaxTableSize == TableSize);
// Create the BB that does the lookups.
Module &Mod = *CommonDest->getParent()->getParent();
@@ -6630,27 +6631,6 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
BranchInst *RangeCheckBranch = nullptr;
- // Grow the table to cover all possible index values to avoid the range check.
- // It will use the default result to fill in the table hole later, so make
- // sure it exist.
- if (UseSwitchConditionAsTableIndex && HasDefaultResults) {
- ConstantRange CR = computeConstantRange(TableIndex, /* ForSigned */ false);
- // Grow the table shouldn't have any size impact by checking
- // WouldFitInRegister.
- // TODO: Consider growing the table also when it doesn't fit in a register
- // if no optsize is specified.
- if (all_of(ResultTypes, [&](const auto &KV) {
- return SwitchLookupTable::WouldFitInRegister(
- DL, CR.getUpper().getLimitedValue(), KV.second /* ResultType */);
- })) {
- // The default branch is unreachable after we enlarge the lookup table.
- // Adjust DefaultIsReachable to reuse code path.
- TableSize = CR.getUpper().getZExtValue();
- DefaultIsReachable = false;
- }
- }
-
- const bool GeneratingCoveredLookupTable = (MaxTableSize == TableSize);
if (!DefaultIsReachable || GeneratingCoveredLookupTable) {
Builder.CreateBr(LookupBB);
if (DTU)
diff --git a/llvm/test/Transforms/SimplifyCFG/switch_mask.ll b/llvm/test/Transforms/SimplifyCFG/switch_mask.ll
index 53ee21eae223c6a..8c97a0660d07074 100644
--- a/llvm/test/Transforms/SimplifyCFG/switch_mask.ll
+++ b/llvm/test/Transforms/SimplifyCFG/switch_mask.ll
@@ -3,18 +3,18 @@
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
-declare i1 @foo()
-
; https://alive2.llvm.org/ce/z/tuxLhJ
define i1 @switch_lookup_with_small_i1(i64 %x) {
; CHECK-LABEL: @switch_lookup_with_small_i1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[AND:%.*]] = and i64 [[X:%.*]], 15
-; CHECK-NEXT: [[SWITCH_CAST:%.*]] = trunc i64 [[AND]] to i16
-; CHECK-NEXT: [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i16 [[SWITCH_CAST]], 1
-; CHECK-NEXT: [[SWITCH_DOWNSHIFT:%.*]] = lshr i16 1030, [[SWITCH_SHIFTAMT]]
-; CHECK-NEXT: [[SWITCH_MASKED:%.*]] = trunc i16 [[SWITCH_DOWNSHIFT]] to i1
-; CHECK-NEXT: ret i1 [[SWITCH_MASKED]]
+; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i64 [[AND]], 11
+; CHECK-NEXT: [[SWITCH_CAST:%.*]] = trunc i64 [[AND]] to i11
+; CHECK-NEXT: [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i11 [[SWITCH_CAST]], 1
+; CHECK-NEXT: [[SWITCH_DOWNSHIFT:%.*]] = lshr i11 -1018, [[SWITCH_SHIFTAMT]]
+; CHECK-NEXT: [[SWITCH_MASKED:%.*]] = trunc i11 [[SWITCH_DOWNSHIFT]] to i1
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[TMP0]], i1 [[SWITCH_MASKED]], i1 false
+; CHECK-NEXT: ret i1 [[TMP1]]
;
entry:
%and = and i64 %x, 15
@@ -37,11 +37,13 @@ define i8 @switch_lookup_with_small_i8(i64 %x) {
; CHECK-LABEL: @switch_lookup_with_small_i8(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[REM:%.*]] = urem i64 [[X:%.*]], 5
-; CHECK-NEXT: [[SWITCH_CAST:%.*]] = trunc i64 [[REM]] to i40
-; CHECK-NEXT: [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i40 [[SWITCH_CAST]], 8
-; CHECK-NEXT: [[SWITCH_DOWNSHIFT:%.*]] = lshr i40 460303, [[SWITCH_SHIFTAMT]]
-; CHECK-NEXT: [[SWITCH_MASKED:%.*]] = trunc i40 [[SWITCH_DOWNSHIFT]] to i8
-; CHECK-NEXT: ret i8 [[SWITCH_MASKED]]
+; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i64 [[REM]], 3
+; CHECK-NEXT: [[SWITCH_CAST:%.*]] = trunc i64 [[REM]] to i24
+; CHECK-NEXT: [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i24 [[SWITCH_CAST]], 8
+; CHECK-NEXT: [[SWITCH_DOWNSHIFT:%.*]] = lshr i24 460303, [[SWITCH_SHIFTAMT]]
+; CHECK-NEXT: [[SWITCH_MASKED:%.*]] = trunc i24 [[SWITCH_DOWNSHIFT]] to i8
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[TMP0]], i8 [[SWITCH_MASKED]], i8 0
+; CHECK-NEXT: ret i8 [[TMP1]]
;
entry:
%rem = urem i64 %x, 5
@@ -105,71 +107,3 @@ lor.end:
%0 = phi i8 [ 15, %sw.bb0 ], [ 6, %sw.bb1 ], [ 7, %sw.bb2 ], [ 0, %default ]
ret i8 %0
}
-
-; Negative test: The default branch is unreachable, also it has no result.
-define i1 @switch_lookup_with_small_i1_default_unreachable(i32 %x) {
-; CHECK-LABEL: @switch_lookup_with_small_i1_default_unreachable(
-; CHECK-NEXT: entry:
-; CHECK-NEXT: [[AND:%.*]] = and i32 [[X:%.*]], 15
-; CHECK-NEXT: ret i1 false
-;
-entry:
- %and = and i32 %x, 15
- switch i32 %and, label %default [
- i32 4, label %phi.end
- i32 2, label %phi.end
- i32 10, label %phi.end
- i32 9, label %phi.end
- i32 1, label %sw.bb1.i
- i32 3, label %sw.bb1.i
- i32 5, label %sw.bb1.i
- i32 0, label %sw.bb1.i
- i32 6, label %sw.bb1.i
- i32 7, label %sw.bb1.i
- i32 8, label %sw.bb1.i
- ]
-
-sw.bb1.i: ; preds = %entry, %entry, %entry, %entry, %entry, %entry, %entry
- br label %phi.end
-
-default: ; preds = %entry
- unreachable
-
-phi.end: ; preds = %sw.bb1.i, %entry, %entry, %entry, %entry
- %retval = phi i1 [ false, %sw.bb1.i ], [ false, %entry ], [ false, %entry ], [ false, %entry ], [ false, %entry ]
- ret i1 %retval
-}
-
-; Negative test: The result in default reachable, but its value is not const.
-define i1 @switch_lookup_with_small_i1_default_nonconst(i64 %x) {
-; CHECK-LABEL: @switch_lookup_with_small_i1_default_nonconst(
-; CHECK-NEXT: entry:
-; CHECK-NEXT: [[AND:%.*]] = and i64 [[X:%.*]], 15
-; CHECK-NEXT: switch i64 [[AND]], label [[DEFAULT:%.*]] [
-; CHECK-NEXT: i64 10, label [[LOR_END:%.*]]
-; CHECK-NEXT: i64 1, label [[LOR_END]]
-; CHECK-NEXT: i64 2, label [[LOR_END]]
-; CHECK-NEXT: ]
-; CHECK: default:
-; CHECK-NEXT: [[CALL:%.*]] = tail call i1 @foo()
-; CHECK-NEXT: br label [[LOR_END]]
-; CHECK: lor.end:
-; CHECK-NEXT: [[TMP0:%.*]] = phi i1 [ true, [[ENTRY:%.*]] ], [ [[CALL]], [[DEFAULT]] ], [ true, [[ENTRY]] ], [ true, [[ENTRY]] ]
-; CHECK-NEXT: ret i1 [[TMP0]]
-;
-entry:
- %and = and i64 %x, 15
- switch i64 %and, label %default [
- i64 10, label %lor.end
- i64 1, label %lor.end
- i64 2, label %lor.end
- ]
-
-default: ; preds = %entry
- %call = tail call i1 @foo()
- br label %lor.end
-
-lor.end: ; preds = %entry, %entry, %entry, %default
- %0 = phi i1 [ true, %entry ], [ %call, %default ], [ true, %entry ], [ true, %entry ]
- ret i1 %0
-}
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