[llvm] 67aec0c - [LowerSwitch] Use unsigned integer for range comparison (#93237)

[via llvm-commits]

Author: Peter Rong
Date: 2024-05-27T10:58:22-07:00
New Revision: 67aec0cd62d607b4e5b7198769be061454ce67b3

URL: https://github.com/llvm/llvm-project/commit/67aec0cd62d607b4e5b7198769be061454ce67b3
DIFF: https://github.com/llvm/llvm-project/commit/67aec0cd62d607b4e5b7198769be061454ce67b3.diff

LOG: [LowerSwitch] Use unsigned integer for range comparison (#93237)

Commit 1db51d8eb2 switched from int64_t to `APInt` to prevent high precision integer overflow.
However, when comparing the "range" of switch cases, we should switch to unsigned integer to prevent overflow.
This patch fixes https://github.com/llvm/llvm-project/issues/93152. 
Some test cases are added.

Signed-off-by: Peter Rong <PeterRong96 at gmail.com>

Added: 
    llvm/test/Transforms/LowerSwitch/93152.ll

Modified: 
    llvm/lib/Transforms/Utils/LowerSwitch.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/LowerSwitch.cpp b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
index f5921e5ccb091..f4ef6d02abf0c 100644
--- a/llvm/lib/Transforms/Utils/LowerSwitch.cpp
+++ b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
@@ -208,7 +208,7 @@ BasicBlock *NewLeafBlock(CaseRange &Leaf, Value *Val, ConstantInt *LowerBound,
     PHINode *PN = cast<PHINode>(I);
     // Remove all but one incoming entries from the cluster
     APInt Range = Leaf.High->getValue() - Leaf.Low->getValue();
-    for (APInt j(Range.getBitWidth(), 0, true); j.slt(Range); ++j) {
+    for (APInt j(Range.getBitWidth(), 0, false); j.ult(Range); ++j) {
       PN->removeIncomingValue(OrigBlock);
     }
 

diff  --git a/llvm/test/Transforms/LowerSwitch/93152.ll b/llvm/test/Transforms/LowerSwitch/93152.ll
new file mode 100644
index 0000000000000..f796b8c7c7821
--- /dev/null
+++ b/llvm/test/Transforms/LowerSwitch/93152.ll
@@ -0,0 +1,97 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=lower-switch -S | FileCheck %s
+define void @i3_range_4(i3 %0) {
+; CHECK-LABEL: define void @i3_range_4(
+; CHECK-SAME: i3 [[TMP0:%.*]]) {
+; CHECK-NEXT:  [[BB_0:.*:]]
+; CHECK-NEXT:    br label %[[LEAFBLOCK:.*]]
+; CHECK:       [[LEAFBLOCK]]:
+; CHECK-NEXT:    [[DOTOFF:%.*]] = add i3 [[TMP0]], 2
+; CHECK-NEXT:    [[SWITCHLEAF:%.*]] = icmp ule i3 [[DOTOFF]], -4
+; CHECK-NEXT:    br i1 [[SWITCHLEAF]], label %[[BB_1:.*]], label %[[BB_2:.*]]
+; CHECK:       [[BB_1]]:
+; CHECK-NEXT:    [[TMP:%.*]] = phi i3 [ 0, %[[LEAFBLOCK]] ]
+; CHECK-NEXT:    br label %[[BB_2]]
+; CHECK:       [[BB_2]]:
+; CHECK-NEXT:    ret void
+;
+bb.0:
+  switch i3 %0, label %bb.2 [
+  i3 -1, label %bb.1
+  i3 -2, label %bb.1
+  i3 2, label %bb.1
+  i3 1, label %bb.1
+  i3 0, label %bb.1
+  ]
+
+bb.1:                                             ; preds = %bb.0, %bb.0, %bb.0, %bb.0, %bb.0
+  %tmp = phi i3 [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ]
+  br label %bb.2
+
+bb.2:                                             ; preds = %bb.1, %bb.0
+  ret void
+}
+
+define void @i3_range_6(i3 %0) {
+; CHECK-LABEL: define void @i3_range_6(
+; CHECK-SAME: i3 [[TMP0:%.*]]) {
+; CHECK-NEXT:  [[BB_0:.*:]]
+; CHECK-NEXT:    br label %[[LEAFBLOCK:.*]]
+; CHECK:       [[LEAFBLOCK]]:
+; CHECK-NEXT:    [[SWITCHLEAF:%.*]] = icmp sge i3 [[TMP0]], -3
+; CHECK-NEXT:    br i1 [[SWITCHLEAF]], label %[[BB_1:.*]], label %[[BB_2:.*]]
+; CHECK:       [[BB_1]]:
+; CHECK-NEXT:    [[TMP:%.*]] = phi i3 [ 0, %[[LEAFBLOCK]] ]
+; CHECK-NEXT:    br label %[[BB_2]]
+; CHECK:       [[BB_2]]:
+; CHECK-NEXT:    ret void
+;
+bb.0:
+  switch i3 %0, label %bb.2 [
+  i3 -1, label %bb.1
+  i3 -2, label %bb.1
+  i3 -3, label %bb.1
+  i3 3, label %bb.1
+  i3 2, label %bb.1
+  i3 1, label %bb.1
+  i3 0, label %bb.1
+  ]
+
+bb.1:                                             ; preds = %bb.0, %bb.0, %bb.0, %bb.0, %bb.0
+  %tmp = phi i3 [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ]
+  br label %bb.2
+
+bb.2:                                             ; preds = %bb.1, %bb.0
+  ret void
+}
+
+
+define void @i3_range_7(i3 %0) {
+; CHECK-LABEL: define void @i3_range_7(
+; CHECK-SAME: i3 [[TMP0:%.*]]) {
+; CHECK-NEXT:  [[BB_0:.*:]]
+; CHECK-NEXT:    br label %[[BB_1:.*]]
+; CHECK:       [[BB_1]]:
+; CHECK-NEXT:    br label %[[BB_2:.*]]
+; CHECK:       [[BB_2]]:
+; CHECK-NEXT:    ret void
+;
+bb.0:
+  switch i3 %0, label %bb.2 [
+  i3 -1, label %bb.1
+  i3 -2, label %bb.1
+  i3 -3, label %bb.1
+  i3 -4, label %bb.1
+  i3 3, label %bb.1
+  i3 2, label %bb.1
+  i3 1, label %bb.1
+  i3 0, label %bb.1
+  ]
+
+bb.1:                                             ; preds = %bb.0, %bb.0, %bb.0, %bb.0, %bb.0
+  %tmp = phi i3 [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ], [ 0, %bb.0 ]
+  br label %bb.2
+
+bb.2:                                             ; preds = %bb.1, %bb.0
+  ret void
+}