[llvm] 9e4f674 - [Test] Add an example of unprofitable PR Phi insertion

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2020-06-15T15:56:06+07:00
New Revision: 9e4f674888d6664d27aae31767f397595b1e2566

URL: https://github.com/llvm/llvm-project/commit/9e4f674888d6664d27aae31767f397595b1e2566
DIFF: https://github.com/llvm/llvm-project/commit/9e4f674888d6664d27aae31767f397595b1e2566.diff

LOG: [Test] Add an example of unprofitable PR Phi insertion

This test demonstrates weird behavior of SimplifyCFG: seems that bigger
size of block leads to worse optimization choice.

Added: 
    llvm/test/Transforms/SimplifyCFG/unprofitable-pr.ll

Modified: 
    

Removed: 
    


################################################################################
diff  --git a/llvm/test/Transforms/SimplifyCFG/unprofitable-pr.ll b/llvm/test/Transforms/SimplifyCFG/unprofitable-pr.ll
new file mode 100644
index 000000000000..461003717797
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/unprofitable-pr.ll
@@ -0,0 +1,108 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -simplifycfg -S < %s | FileCheck %s
+; RUN: opt -passes=simplify-cfg -S < %s | FileCheck %s
+
+target datalayout = "e-p:64:64-p5:32:32-A5"
+
+declare void @llvm.assume(i1)
+
+define void @test_01(i1 %c, i64* align 1 %ptr) local_unnamed_addr #0 {
+; CHECK-LABEL: @test_01(
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[TRUE2_CRITEDGE:%.*]], label [[FALSE1:%.*]]
+; CHECK:       false1:
+; CHECK-NEXT:    store volatile i64 1, i64* [[PTR:%.*]], align 4
+; CHECK-NEXT:    [[PTRINT:%.*]] = ptrtoint i64* [[PTR]] to i64
+; CHECK-NEXT:    [[MASKEDPTR:%.*]] = and i64 [[PTRINT]], 7
+; CHECK-NEXT:    [[MASKCOND:%.*]] = icmp eq i64 [[MASKEDPTR]], 0
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
+; CHECK-NEXT:    store volatile i64 0, i64* [[PTR]], align 8
+; CHECK-NEXT:    store volatile i64 3, i64* [[PTR]], align 8
+; CHECK-NEXT:    ret void
+; CHECK:       true2.critedge:
+; CHECK-NEXT:    [[PTRINT_C:%.*]] = ptrtoint i64* [[PTR]] to i64
+; CHECK-NEXT:    [[MASKEDPTR_C:%.*]] = and i64 [[PTRINT_C]], 7
+; CHECK-NEXT:    [[MASKCOND_C:%.*]] = icmp eq i64 [[MASKEDPTR_C]], 0
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND_C]])
+; CHECK-NEXT:    store volatile i64 0, i64* [[PTR]], align 8
+; CHECK-NEXT:    store volatile i64 2, i64* [[PTR]], align 8
+; CHECK-NEXT:    ret void
+;
+  br i1 %c, label %true1, label %false1
+
+true1:                                            ; preds = %false1, %0
+  %ptrint = ptrtoint i64* %ptr to i64
+  %maskedptr = and i64 %ptrint, 7
+  %maskcond = icmp eq i64 %maskedptr, 0
+  tail call void @llvm.assume(i1 %maskcond)
+  store volatile i64 0, i64* %ptr, align 8
+  br i1 %c, label %true2, label %false2
+
+false1:                                           ; preds = %0
+  store volatile i64 1, i64* %ptr, align 4
+  br label %true1
+
+true2:                                            ; preds = %true1
+  store volatile i64 2, i64* %ptr, align 8
+  ret void
+
+false2:                                           ; preds = %true1
+  store volatile i64 3, i64* %ptr, align 8
+  ret void
+}
+
+; FIXME: SimplifyCFG is doing something weird here. It should have split the
+; blocks like in the test above, but instead it creates .pr Phi node which
+; only complicates things.
+define void @test_02(i1 %c, i64* align 1 %ptr) local_unnamed_addr #0 {
+; CHECK-LABEL: @test_02(
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[TRUE1:%.*]], label [[FALSE1:%.*]]
+; CHECK:       true1:
+; CHECK-NEXT:    [[C_PR:%.*]] = phi i1 [ [[C]], [[FALSE1]] ], [ true, [[TMP0:%.*]] ]
+; CHECK-NEXT:    [[PTRINT:%.*]] = ptrtoint i64* [[PTR:%.*]] to i64
+; CHECK-NEXT:    [[MASKEDPTR:%.*]] = and i64 [[PTRINT]], 7
+; CHECK-NEXT:    [[MASKCOND:%.*]] = icmp eq i64 [[MASKEDPTR]], 0
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[MASKCOND]])
+; CHECK-NEXT:    store volatile i64 0, i64* [[PTR]], align 8
+; CHECK-NEXT:    store volatile i64 -1, i64* [[PTR]], align 8
+; CHECK-NEXT:    store volatile i64 -1, i64* [[PTR]], align 8
+; CHECK-NEXT:    store volatile i64 -1, i64* [[PTR]], align 8
+; CHECK-NEXT:    store volatile i64 -1, i64* [[PTR]], align 8
+; CHECK-NEXT:    store volatile i64 -1, i64* [[PTR]], align 8
+; CHECK-NEXT:    br i1 [[C_PR]], label [[TRUE2:%.*]], label [[FALSE2:%.*]]
+; CHECK:       false1:
+; CHECK-NEXT:    store volatile i64 1, i64* [[PTR]], align 4
+; CHECK-NEXT:    br label [[TRUE1]]
+; CHECK:       true2:
+; CHECK-NEXT:    store volatile i64 2, i64* [[PTR]], align 8
+; CHECK-NEXT:    ret void
+; CHECK:       false2:
+; CHECK-NEXT:    store volatile i64 3, i64* [[PTR]], align 8
+; CHECK-NEXT:    ret void
+;
+  br i1 %c, label %true1, label %false1
+
+true1:                                            ; preds = %false1, %0
+  %ptrint = ptrtoint i64* %ptr to i64
+  %maskedptr = and i64 %ptrint, 7
+  %maskcond = icmp eq i64 %maskedptr, 0
+  tail call void @llvm.assume(i1 %maskcond)
+  store volatile i64 0, i64* %ptr, align 8
+  store volatile i64 -1, i64* %ptr, align 8
+  store volatile i64 -1, i64* %ptr, align 8
+  store volatile i64 -1, i64* %ptr, align 8
+  store volatile i64 -1, i64* %ptr, align 8
+  store volatile i64 -1, i64* %ptr, align 8
+  br i1 %c, label %true2, label %false2
+
+false1:                                           ; preds = %0
+  store volatile i64 1, i64* %ptr, align 4
+  br label %true1
+
+true2:                                            ; preds = %true1
+  store volatile i64 2, i64* %ptr, align 8
+  ret void
+
+false2:                                           ; preds = %true1
+  store volatile i64 3, i64* %ptr, align 8
+  ret void
+}