[llvm] fae7deb - [CHR] Don't run ControlHeightReduction if any BB has address taken

Sat Jun 12 10:30:00 PDT 2021

Author: Xun Li
Date: 2021-06-12T10:29:53-07:00
New Revision: fae7debadcea335d4aaddee82406a8d10426e730

URL: https://github.com/llvm/llvm-project/commit/fae7debadcea335d4aaddee82406a8d10426e730
DIFF: https://github.com/llvm/llvm-project/commit/fae7debadcea335d4aaddee82406a8d10426e730.diff

LOG: [CHR] Don't run ControlHeightReduction if any BB has address taken

This patch is to address https://bugs.llvm.org/show_bug.cgi?id=50610.
In computed goto pattern, there are usually a list of basic blocks that are all targets of indirectbr instruction, and each basic block also has address taken and stored in a variable.
CHR pass could potentially clone these basic blocks, which would generate a cloned version of the indirectbr and clonved version of all basic blocks in the list.
However these basic blocks will not have their addresses taken and stored anywhere. So latter SimplifyCFG pass will simply remove all tehse cloned basic blocks, resulting in incorrect code.
To fix this, when searching for scopes, we skip scopes that contains BBs with addresses taken.
Added a few test cases.

Reviewed By: aeubanks, wenlei, hoy

Differential Revision: https://reviews.llvm.org/D103867

Added: 
    

Modified: 
    llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
    llvm/test/Transforms/PGOProfile/chr.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp b/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
index 34202562c8bce..3b4d80dc80232 100644

--- a/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
+++ b/llvm/lib/Transforms/Instrumentation/ControlHeightReduction.cpp
@@ -767,6 +767,11 @@ CHRScope * CHR::findScope(Region *R) {
   for (BasicBlock *Pred : predecessors(Entry))
     if (R->contains(Pred))
       return nullptr;
+  // If any of the basic blocks have address taken, we must skip this region
+  // because we cannot clone basic blocks that have address taken.
+  for (BasicBlock *BB : R->blocks())
+    if (BB->hasAddressTaken())
+      return nullptr;
   if (Exit) {
     // Try to find an if-then block (check if R is an if-then).
     // if (cond) {

diff  --git a/llvm/test/Transforms/PGOProfile/chr.ll b/llvm/test/Transforms/PGOProfile/chr.ll
index 7dd9de041a1ac..6a95c68c5f139 100644
--- a/llvm/test/Transforms/PGOProfile/chr.ll
+++ b/llvm/test/Transforms/PGOProfile/chr.ll
@@ -2527,6 +2527,122 @@ bb3:
   ret void
 }
 
+; Test that chr will skip this function when addresses are taken on basic blocks.
+ at gototable1 = weak_odr dso_local local_unnamed_addr constant [2 x i8*] [i8* blockaddress(@test_chr_with_bbs_address_taken1, %bb3), i8* blockaddress(@test_chr_with_bbs_address_taken1, %bb3)]
+define void @test_chr_with_bbs_address_taken1(i32* %i) !prof !14 {
+; CHECK-LABEL: @test_chr_with_bbs_address_taken1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* [[I:%.*]], align 4
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[TMP0]], 1
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP1]], 0
+; CHECK-NEXT:    br i1 [[TMP2]], label [[BB1:%.*]], label [[BB0:%.*]], !prof [[PROF16]]
+; CHECK:       bb0:
+; CHECK-NEXT:    call void @foo()
+; CHECK-NEXT:    br label [[BB1]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[TMP3:%.*]] = and i32 [[TMP0]], 2
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[TMP4]], label [[BB4:%.*]], label [[BB2:%.*]], !prof [[PROF16]]
+; CHECK:       bb2:
+; CHECK-NEXT:    call void @foo()
+; CHECK-NEXT:    br label [[BB4]]
+; CHECK:       bb4:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %0 = load i32, i32* %i
+  %1 = and i32 %0, 1
+  %2 = icmp eq i32 %1, 0
+  br i1 %2, label %bb1, label %bb0, !prof !15
+
+bb0:
+  call void @foo()
+  br label %bb1
+
+bb1:
+  %3 = and i32 %0, 2
+  %4 = icmp eq i32 %3, 0
+  br i1 %4, label %bb4, label %bb2, !prof !15
+
+bb2:
+  call void @foo()
+  %pc = bitcast i32* %i to i8*
+  indirectbr i8* %pc, [label %bb3, label %bb3]
+
+bb3:
+  br label %bb4
+
+bb4:
+  ret void
+}
+
+; Test that chr will still optimize the first 2 regions,
+; but will skip the last one due to basic blocks have address taken.
+ at gototable2 = weak_odr dso_local local_unnamed_addr constant [2 x i8*] [i8* blockaddress(@test_chr_with_bbs_address_taken2, %bb5), i8* blockaddress(@test_chr_with_bbs_address_taken2, %bb5)]
+define void @test_chr_with_bbs_address_taken2(i32* %i) !prof !14 {
+; CHECK-LABEL: @test_chr_with_bbs_address_taken2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* [[I:%.*]], align 4
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[TMP0]], 3
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp eq i32 [[TMP1]], 3
+; CHECK-NEXT:    br i1 [[TMP2]], label [[BB0:%.*]], label [[ENTRY_SPLIT_NONCHR:%.*]], !prof [[PROF15]]
+; CHECK:       bb0:
+; CHECK-NEXT:    call void @foo()
+; CHECK-NEXT:    call void @foo()
+; CHECK-NEXT:    br label [[BB3:%.*]]
+; CHECK:       entry.split.nonchr:
+; CHECK-NEXT:    [[TMP3:%.*]] = and i32 [[TMP0]], 1
+; CHECK-NEXT:    [[DOTNOT:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[DOTNOT]], label [[BB1_NONCHR:%.*]], label [[BB0_NONCHR:%.*]], !prof [[PROF16]]
+; CHECK:       bb0.nonchr:
+; CHECK-NEXT:    call void @foo()
+; CHECK-NEXT:    br label [[BB1_NONCHR]]
+; CHECK:       bb1.nonchr:
+; CHECK-NEXT:    [[TMP4:%.*]] = and i32 [[TMP0]], 2
+; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[TMP4]], 0
+; CHECK-NEXT:    br i1 [[TMP5]], label [[BB3]], label [[BB2_NONCHR:%.*]], !prof [[PROF16]]
+; CHECK:       bb2.nonchr:
+; CHECK-NEXT:    call void @foo()
+; CHECK-NEXT:    br label [[BB3]]
+; CHECK:       bb3:
+; CHECK-NEXT:    ret void
+;
+entry:
+  %0 = load i32, i32* %i
+  %1 = and i32 %0, 1
+  %2 = icmp eq i32 %1, 0
+  br i1 %2, label %bb1, label %bb0, !prof !15
+
+bb0:
+  call void @foo()
+  br label %bb1
+
+bb1:
+  %3 = and i32 %0, 2
+  %4 = icmp eq i32 %3, 0
+  br i1 %4, label %bb3, label %bb2, !prof !15
+
+bb2:
+  call void @foo()
+  br label %bb3
+
+bb3:
+  %5 = and i32 %0, 2
+  %6 = icmp eq i32 %5, 0
+  br i1 %6, label %bb6, label %bb4, !prof !15
+
+bb4:
+  %pc = bitcast i32* %i to i8*
+  indirectbr i8* %pc, [label %bb5, label %bb5]
+
+bb5:
+  br label %bb6
+
+bb6:
+  ret void
+}
+
+
 !llvm.module.flags = !{!0}
 !0 = !{i32 1, !"ProfileSummary", !1}
 !1 = !{!2, !3, !4, !5, !6, !7, !8, !9}


        
