[MachinePipeliner] Avoid indeterminate order in FuncUnitSorter

Summary:
This is exposed by adding a new testcase in PowerPC in
https://reviews.llvm.org/rL367732

The testcase got different output on different platform, hence breaking
buildbots.

The problem is that we get differnt FuncUnitOrder when calculateResMII.

The root cause is:
1. Two MachineInstr might get SAME priority(MFUsx) from minFuncUnits.
2. Current comparison operator() will return `MFUs1 > MFUs2`.
3. We use iterators for MachineInstr, so the input to FuncUnitSorter
   might be different on differnt platform due to the iterator nature.

So for two MI with same MFU, their order is actually depends on the
iterator order, which is platform (implemtation) dependent.

This is risky, and may cause cross-compiling problems.

The fix is to check make sure we assign a determine order when they are
equal.

Reviewers: bcahoon, hfinkel, jmolloy

Subscribers: nemanjai, hiraditya, MaskRay, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65992

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368441 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachinePipeliner.cpp

@@ -958,7 +958,7 @@ struct FuncUnitSorter {
     unsigned F1 = 0, F2 = 0;
     unsigned MFUs1 = minFuncUnits(IS1, F1);
     unsigned MFUs2 = minFuncUnits(IS2, F2);
-    if (MFUs1 == 1 && MFUs2 == 1)
+    if (MFUs1 == MFUs2)
       return Resources.lookup(F1) < Resources.lookup(F2);
     return MFUs1 > MFUs2;
   }

test/CodeGen/PowerPC/sms-cpy-1.ll

@@ -0,0 +1,116 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -verify-machineinstrs\
+; RUN:       -mcpu=pwr9 --ppc-enable-pipeliner 2>&1 | FileCheck %s
+
+@.str.28 = external unnamed_addr constant [69 x i8], align 1
+
+define void @print_res() unnamed_addr {
+; CHECK-LABEL: print_res:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    mflr 0
+; CHECK-NEXT:    std 0, 16(1)
+; CHECK-NEXT:    stdu 1, -128(1)
+; CHECK-NEXT:    .cfi_def_cfa_offset 128
+; CHECK-NEXT:    .cfi_offset lr, 16
+; CHECK-NEXT:    lwz 3, 0(3)
+; CHECK-NEXT:    addi 3, 3, -1
+; CHECK-NEXT:    clrldi 4, 3, 32
+; CHECK-NEXT:    cmplwi 0, 3, 1
+; CHECK-NEXT:    li 3, 1
+; CHECK-NEXT:    isel 3, 4, 3, 1
+; CHECK-NEXT:    li 4, 2
+; CHECK-NEXT:    addi 3, 3, -1
+; CHECK-NEXT:    cmpldi 3, 2
+; CHECK-NEXT:    isel 3, 3, 4, 0
+; CHECK-NEXT:    li 4, 0
+; CHECK-NEXT:    addi 3, 3, 1
+; CHECK-NEXT:    li 5, 0
+; CHECK-NEXT:    li 7, -1
+; CHECK-NEXT:    mtctr 3
+; CHECK-NEXT:    lbz 5, 0(5)
+; CHECK-NEXT:    li 3, 1
+; CHECK-NEXT:    bdz .LBB0_6
+; CHECK-NEXT:  # %bb.1:
+; CHECK-NEXT:    xori 6, 5, 84
+; CHECK-NEXT:    clrldi 5, 7, 32
+; CHECK-NEXT:    lbz 5, 0(5)
+; CHECK-NEXT:    addi 3, 3, 1
+; CHECK-NEXT:    addi 8, 7, -1
+; CHECK-NEXT:    bdz .LBB0_5
+; CHECK-NEXT:  # %bb.2:
+; CHECK-NEXT:    cntlzw 6, 6
+; CHECK-NEXT:    srwi 7, 6, 5
+; CHECK-NEXT:    xori 6, 5, 84
+; CHECK-NEXT:    clrldi 5, 8, 32
+; CHECK-NEXT:    addi 8, 8, -1
+; CHECK-NEXT:    lbz 5, 0(5)
+; CHECK-NEXT:    addi 3, 3, 1
+; CHECK-NEXT:    bdz .LBB0_4
+; CHECK-NEXT:    .p2align 4
+; CHECK-NEXT:  .LBB0_3: #
+; CHECK-NEXT:    clrldi 10, 8, 32
+; CHECK-NEXT:    cntlzw 9, 6
+; CHECK-NEXT:    xori 6, 5, 84
+; CHECK-NEXT:    lbz 5, 0(10)
+; CHECK-NEXT:    addi 8, 8, -1
+; CHECK-NEXT:    addi 3, 3, 1
+; CHECK-NEXT:    add 4, 4, 7
+; CHECK-NEXT:    srwi 7, 9, 5
+; CHECK-NEXT:    bdnz .LBB0_3
+; CHECK-NEXT:  .LBB0_4:
+; CHECK-NEXT:    add 4, 4, 7
+; CHECK-NEXT:  .LBB0_5:
+; CHECK-NEXT:    cntlzw 6, 6
+; CHECK-NEXT:    srwi 6, 6, 5
+; CHECK-NEXT:    add 4, 4, 6
+; CHECK-NEXT:  .LBB0_6:
+; CHECK-NEXT:    xori 5, 5, 84
+; CHECK-NEXT:    cntlzw 5, 5
+; CHECK-NEXT:    clrldi 3, 3, 32
+; CHECK-NEXT:    std 3, 104(1)
+; CHECK-NEXT:    addis 3, 2, .LC0@toc@ha
+; CHECK-NEXT:    ld 3, .LC0@toc@l(3)
+; CHECK-NEXT:    li 7, 0
+; CHECK-NEXT:    li 8, 3
+; CHECK-NEXT:    srwi 5, 5, 5
+; CHECK-NEXT:    add 4, 4, 5
+; CHECK-NEXT:    li 5, 0
+; CHECK-NEXT:    std 5, 120(1)
+; CHECK-NEXT:    li 5, 3
+; CHECK-NEXT:    std 5, 96(1)
+; CHECK-NEXT:    clrldi 6, 4, 32
+; CHECK-NEXT:    li 4, 3
+; CHECK-NEXT:    li 5, 0
+; CHECK-NEXT:    li 10, 0
+; CHECK-NEXT:    bl printf
+; CHECK-NEXT:    nop
+  %1 = load i32, i32* undef, align 4
+  %2 = add i32 %1, -1
+  %3 = zext i32 %2 to i64
+  %4 = zext i32 3 to i64
+  br label %5
+
+5:                                                ; preds = %5, %0
+  %6 = phi i64 [ %16, %5 ], [ 0, %0 ]
+  %7 = phi i32 [ %15, %5 ], [ 0, %0 ]
+  %8 = trunc i64 %6 to i32
+  %9 = sub i32 0, %8
+  %10 = zext i32 %9 to i64
+  %11 = getelementptr inbounds i8, i8* null, i64 %10
+  %12 = load i8, i8* %11, align 1
+  %13 = icmp eq i8 %12, 84
+  %14 = zext i1 %13 to i32
+  %15 = add i32 %7, %14
+  %16 = add nuw nsw i64 %6, 1
+  %17 = icmp ult i64 %16, %3
+  %18 = icmp ult i64 %16, %4
+  %19 = and i1 %18, %17
+  br i1 %19, label %5, label %20
+
+20:                                               ; preds = %5
+  %21 = trunc i64 %16 to i32
+  call void (i8*, ...) @printf(i8* getelementptr inbounds ([69 x i8], [69 x i8]* @.str.28, i64 0, i64 0), i32 zeroext 3, i32 zeroext undef, i32 zeroext %15, i32 zeroext undef, i32 zeroext 3, i8* undef, i32 zeroext undef, i32 zeroext 3, i32 zeroext %21, i8* undef, i32 zeroext undef) #1
+  unreachable
+}
+
+declare void @printf(i8*, ...) local_unnamed_addr #0