[llvm] 18b3415 - [Test] Add a test demonstrating a missing opportunity to PRE a load

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2021-03-30T12:29:11+07:00
New Revision: 18b3415e615b7f7b9a2113ff6f25facab02a40b7

URL: https://github.com/llvm/llvm-project/commit/18b3415e615b7f7b9a2113ff6f25facab02a40b7
DIFF: https://github.com/llvm/llvm-project/commit/18b3415e615b7f7b9a2113ff6f25facab02a40b7.diff

LOG: [Test] Add a test demonstrating a missing opportunity to PRE a load

Added: 
    llvm/test/Transforms/GVN/PRE/pre-aliasning-path.ll

Modified: 
    

Removed: 
    


################################################################################
diff  --git a/llvm/test/Transforms/GVN/PRE/pre-aliasning-path.ll b/llvm/test/Transforms/GVN/PRE/pre-aliasning-path.ll
new file mode 100644
index 0000000000000..73af4ad9cd76f
--- /dev/null
+++ b/llvm/test/Transforms/GVN/PRE/pre-aliasning-path.ll
@@ -0,0 +1,148 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -basic-aa -enable-load-pre -enable-pre -gvn -S < %s | FileCheck %s
+
+declare void @side_effect_0()
+
+declare void @side_effect_1(i32 %x)
+
+declare void @no_side_effect() readonly
+
+; TODO: We can PRE the load into the cold path, removing it from the hot path.
+define i32 @test_01(i32* %p) {
+; CHECK-LABEL: @test_01(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[X:%.*]] = load i32, i32* [[P:%.*]], align 4
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i32 [[X]], 100
+; CHECK-NEXT:    br i1 [[COND]], label [[HOT_PATH:%.*]], label [[COLD_PATH:%.*]]
+; CHECK:       hot_path:
+; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK:       cold_path:
+; CHECK-NEXT:    call void @side_effect_0()
+; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK:       backedge:
+; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], [[X]]
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV_NEXT]], 1000
+; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i32 [[X]]
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i32 [ 0, %entry], [%iv.next, %backedge]
+  %x = load i32, i32* %p
+  %cond = icmp ult i32 %x, 100
+  br i1 %cond, label %hot_path, label %cold_path
+
+hot_path:
+  br label %backedge
+
+cold_path:
+  call void @side_effect_0()
+  br label %backedge
+
+backedge:
+  %iv.next = add i32 %iv, %x
+  %loop.cond = icmp ult i32 %iv.next, 1000
+  br i1 %loop.cond, label %loop, label %exit
+
+exit:
+  ret i32 %x
+}
+
+; TODO: We can PRE the load into the cold path, removing it from the hot path.
+define i32 @test_02(i32* %p) {
+; CHECK-LABEL: @test_02(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[X:%.*]] = load i32, i32* [[P:%.*]], align 4
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i32 [[X]], 100
+; CHECK-NEXT:    br i1 [[COND]], label [[HOT_PATH:%.*]], label [[COLD_PATH:%.*]]
+; CHECK:       hot_path:
+; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK:       cold_path:
+; CHECK-NEXT:    call void @side_effect_1(i32 [[X]])
+; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK:       backedge:
+; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], [[X]]
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV_NEXT]], 1000
+; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i32 [[X]]
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i32 [ 0, %entry], [%iv.next, %backedge]
+  %x = load i32, i32* %p
+  %cond = icmp ult i32 %x, 100
+  br i1 %cond, label %hot_path, label %cold_path
+
+hot_path:
+  br label %backedge
+
+cold_path:
+  call void @side_effect_1(i32 %x)
+  br label %backedge
+
+backedge:
+  %iv.next = add i32 %iv, %x
+  %loop.cond = icmp ult i32 %iv.next, 1000
+  br i1 %loop.cond, label %loop, label %exit
+
+exit:
+  ret i32 %x
+}
+
+define i32 @test_03(i32* %p) {
+; CHECK-LABEL: @test_03(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[X_PRE:%.*]] = load i32, i32* [[P:%.*]], align 4
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[COND:%.*]] = icmp ult i32 [[X_PRE]], 100
+; CHECK-NEXT:    br i1 [[COND]], label [[HOT_PATH:%.*]], label [[COLD_PATH:%.*]]
+; CHECK:       hot_path:
+; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK:       cold_path:
+; CHECK-NEXT:    call void @no_side_effect()
+; CHECK-NEXT:    br label [[BACKEDGE]]
+; CHECK:       backedge:
+; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], [[X_PRE]]
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV_NEXT]], 1000
+; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret i32 [[X_PRE]]
+;
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i32 [ 0, %entry], [%iv.next, %backedge]
+  %x = load i32, i32* %p
+  %cond = icmp ult i32 %x, 100
+  br i1 %cond, label %hot_path, label %cold_path
+
+hot_path:
+  br label %backedge
+
+cold_path:
+  call void @no_side_effect()
+  br label %backedge
+
+backedge:
+  %iv.next = add i32 %iv, %x
+  %loop.cond = icmp ult i32 %iv.next, 1000
+  br i1 %loop.cond, label %loop, label %exit
+
+exit:
+  ret i32 %x
+}