non-determinism regression exposed by f1b0a544514f3d343f32a41de9d6fb0b6cbb6021

[ZequanWu]

f1b0a54 exposed a non-determinism on opt.

To repro, build opt at trunk and use different allocators between two runs:

$ opt -O2 -S reduced.ll -o opt.ll -opt-bisect-limit=382
$ LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libtcmalloc.so.4 opt -O2 -S reduced.ll -o opt.ll.2 -opt-bisect-limit=382
$ diff opt.ll opt.ll.2

reduced.ll:

target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

$_ZN2v84base11CheckGEImplIiiEEPNSt4__Cr12basic_stringIcNS2_11char_traitsIcEENS2_9allocatorIcEEEET_T0_PKc = comdat any

; Function Attrs: nocallback nofree nosync nounwind willreturn memory(none)
declare i64 @llvm.expect.i64(i64, i64) #0

; Function Attrs: null_pointer_is_valid
define linkonce_odr ptr @_ZN2v84base11CheckGEImplIiiEEPNSt4__Cr12basic_stringIcNS2_11char_traitsIcEENS2_9allocatorIcEEEET_T0_PKc(i32 %0, i32 %1, ptr %2) #1 comdat {
  %4 = call i1 @_ZN2v84base9CmpGEImplIiiEENSt4__Cr9enable_ifIXaantsr21is_signed_vs_unsignedIT_T0_EE5valuentsr21is_unsigned_vs_signedIS4_S5_EE5valueEbE4typeES4_S5_(i32 %0)
  br i1 %4, label %7, label %5

5:                                                ; preds = %3
  %6 = load ptr, ptr null, align 8
  br label %7

7:                                                ; preds = %5, %3
  %8 = phi ptr [ %6, %5 ], [ null, %3 ]
  ret ptr %8
}

define i64 @_ZN2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE11PaddingSizeEv() {
  %1 = call i32 @_Z7RoundUpILl4EiET0_S0_()
  %2 = sext i32 %1 to i64
  ret i64 %2
}

; Function Attrs: null_pointer_is_valid
define i32 @_ZN2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE20DataTableStartOffsetEv() #1 {
  %1 = call i64 @_ZN2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE11PaddingSizeEv()
  %2 = trunc i64 %1 to i32
  ret i32 %2
}

; Function Attrs: null_pointer_is_valid
define i32 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE8CapacityEv(i32 %0) #1 {
  %2 = call i32 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE15NumberOfBucketsEv()
  %3 = call ptr @_ZN2v84base11CheckGEImplIiiEEPNSt4__Cr12basic_stringIcNS2_11char_traitsIcEENS2_9allocatorIcEEEET_T0_PKc(i32 %0, i32 0, ptr null)
  %.not = icmp eq ptr %3, null
  br i1 %.not, label %6, label %4

4:                                                ; preds = %1
  %5 = load volatile ptr, ptr null, align 8
  br label %6

6:                                                ; preds = %4, %1
  %7 = call ptr @_ZN2v84base11CheckLEImplIiiEEPNSt4__Cr12basic_stringIcNS2_11char_traitsIcEENS2_9allocatorIcEEEET_T0_PKc(i32 %0)
  ret i32 0
}

define ptr @_ZN2v84base11CheckLEImplIiiEEPNSt4__Cr12basic_stringIcNS2_11char_traitsIcEENS2_9allocatorIcEEEET_T0_PKc(i32 %0) {
  %2 = call i1 @_ZN2v84base9CmpLEImplIiiEENSt4__Cr9enable_ifIXaantsr21is_signed_vs_unsignedIT_T0_EE5valuentsr21is_unsigned_vs_signedIS4_S5_EE5valueEbE4typeES4_S5_(i32 %0)
  %3 = zext i1 %2 to i64
  %4 = call i64 @llvm.expect.i64(i64 %3, i64 1)
  %.not = icmp eq i64 %4, 0
  br i1 %.not, label %5, label %common.ret

common.ret:                                       ; preds = %5, %1
  ret ptr null

5:                                                ; preds = %1
  %6 = load volatile ptr, ptr null, align 8
  br label %common.ret
}

define i1 @_ZN2v84base9CmpGEImplIiiEENSt4__Cr9enable_ifIXaantsr21is_signed_vs_unsignedIT_T0_EE5valuentsr21is_unsigned_vs_signedIS4_S5_EE5valueEbE4typeES4_S5_(i32 %0) {
  %2 = icmp sgt i32 %0, 0
  ret i1 %2
}

; Function Attrs: null_pointer_is_valid
define i32 @_Z7RoundUpILl4EiET0_S0_() #1 {
  %1 = load i32, ptr null, align 4
  ret i32 %1
}

define i1 @_ZN2v84base9CmpLEImplIiiEENSt4__Cr9enable_ifIXaantsr21is_signed_vs_unsignedIT_T0_EE5valuentsr21is_unsigned_vs_signedIS4_S5_EE5valueEbE4typeES4_S5_(i32 %0) {
  %2 = icmp slt i32 %0, 2
  ret i1 %2
}

; Function Attrs: null_pointer_is_valid
define i8 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE7getByteEii() #1 {
  store i32 1, ptr null, align 4
  %1 = call i32 @_ZN2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE20DataTableStartOffsetEv()
  %2 = icmp sgt i32 %1, 0
  br i1 %2, label %.critedge, label %3

3:                                                ; preds = %0
  %4 = load i32, ptr null, align 4
  %5 = call i32 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE21GetBucketsStartOffsetEv()
  %6 = icmp sgt i32 %4, 0
  br i1 %6, label %.critedge, label %7

7:                                                ; preds = %3
  call void null(ptr null, i32 0, ptr null)
  br label %.critedge

.critedge:                                        ; preds = %7, %3, %0
  ret i8 0
}

define i32 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE21GetBucketsStartOffsetEv() {
  %1 = call i32 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE8CapacityEv(i32 0)
  ret i32 0
}

define i32 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE15NumberOfBucketsEv() {
  %1 = call i8 @_ZNK2v88internal21SmallOrderedHashTableINS0_26SmallOrderedNameDictionaryEE7getByteEii()
  ret i32 0
}

attributes #0 = { nocallback nofree nosync nounwind willreturn memory(none) }
attributes #1 = { null_pointer_is_valid }

@jmorse sent a #77774 to fix it.