[FileCheck] Enforce --allow-unused-prefixes=false for llvm/test/Transforms

[mtrofin]

Summary

Explicitly opt-out llvm/test/Transforms/Attributor.

Verified by flipping the default value of allow-unused-prefixes and
observing that none of the failures were under llvm/test/Transforms.

[jhenderson]

llvm/test/Transforms/LoopIdiom/X86/left-shift-until-bittest.ll

38

ALL%s? This doesn't look right to me...

[mtrofin]

fixed update_test_prefix.py and 2 tests

[mtrofin]

llvm/test/Transforms/LoopIdiom/X86/left-shift-until-bittest.ll

38

Thanks for the catch - added fix to update_test_prefix.py. What was happening was: that script tries to clean up cases where, after removing unused prefixes, we're left with one prefix. If the FileCheck was written with %s after the check-prefixes argument, it would consume the space between the prefix and %s, resulting in (for example) "--check-prefix=ALL%s". I fixed by hand a few of these cases, but didn't notice there could be a follow-up behavior: if the test had this "NOTE: Assertions have been autogenerated...", update_test_prefix would also re-run the autogenerator. In this case, that's update_test_checks.py, which would notice the new prefix (ALL%s), and insert checks for it.

The update to update_test_prefix.py is here for reference, I'll patch it separately, then rebase this change. Added @pengfei for that part, to make sure I haven't missed something.

[pengfei]

Glad to see you are using the script. I'm not very sure its behavior. Please pay attention to its changes especially marked CHANGE

llvm/utils/update_test_prefix.py

22 ↗

(On Diff #308984)

I think we just need to add a space for it:

s = re.sub('-?-check-prefixes=([^, ]+) ', '--check-prefix=\\1 ', s)

I once worried we may leave space at the end but didn't consider %s case.
\w+ is not always correct because many prefixes are using - in them.

[mtrofin]

In D92404#2430040, @pengfei wrote:

Glad to see you are using the script. I'm not very sure its behavior. Please pay attention to its changes especially marked CHANGE

Yup, the tool is super-useful, thanks again!

[mtrofin]

In D92404#2430040, @pengfei wrote:

Glad to see you are using the script. I'm not very sure its behavior. Please pay attention to its changes especially marked CHANGE

llvm/utils/update_test_prefix.py

22 ↗

(On Diff #308984)

how about

s = re.sub('-?-check-prefixes=([\w_-]+)', '--check-prefix=\\1', s)

So it'd avoid the extra space, too? Or do we allow other characters?

[pengfei]

Cheers~

llvm/utils/update_test_prefix.py

22 ↗

(On Diff #308984)

I might tend to conservative. As far as I can see it, [\w-] should be Okay. But you need to check the last character is '\n' or ' '. Otherwise it will turn somthing -check-prefixes=A,B into -check-prefix=A,B. Maybe you can use below:

s = re.sub('-?-check-prefixes=([\w-]+\s)', '--check-prefix=\\1', s)

[mtrofin]

llvm/utils/update_test_prefix.py

22 ↗

(On Diff #308984)

sg, I'll send a separate patch with that.

[mtrofin]

separated change to update_test_prefix.py in D92542

[jhenderson]

I don't know anything about the Transform tests, so I don't feel qualified to further review whether what has been done is valid. Hopefully somebody else will be able to review.

[mtrofin]

Added a few more based on recent changes to relevant files - ptal. Thanks!

[lebedev.ri]

IMO this whole direction is wrong, but i'll guess i'll just have to suffer with new reality.

[mtrofin]

In D92404#2431929, @lebedev.ri wrote:

IMO this whole direction is wrong, but i'll guess i'll just have to suffer with new reality.

Not sure what direction you're referring to - if it's about handing unused prefixes, could you please contribute to the RFC thread (http://lists.llvm.org/pipermail/llvm-dev/2020-October/146162.html), it would be helpful to understand what tradeoffs we may have missed.

Thanks!

[lebedev.ri]

In D92404#2432042, @mtrofin wrote:

In D92404#2431929, @lebedev.ri wrote:

IMO this whole direction is wrong, but i'll guess i'll just have to suffer with new reality.

Not sure what direction you're referring to - if it's about handing unused prefixes,

Yep, precisely that direction.

could you please contribute to the RFC thread (http://lists.llvm.org/pipermail/llvm-dev/2020-October/146162.html), it would be helpful to understand what tradeoffs we may have missed.

Thanks!

I have not kept track of that RFC so i'm not sure if i'm just being picky because i'm not aware of a very good reasons pointed out there.

[mtrofin]

In D92404#2432190, @lebedev.ri wrote:

In D92404#2432042, @mtrofin wrote:

In D92404#2431929, @lebedev.ri wrote:

IMO this whole direction is wrong, but i'll guess i'll just have to suffer with new reality.

Not sure what direction you're referring to - if it's about handing unused prefixes,

Yep, precisely that direction.

could you please contribute to the RFC thread (http://lists.llvm.org/pipermail/llvm-dev/2020-October/146162.html), it would be helpful to understand what tradeoffs we may have missed.

Thanks!

I have not kept track of that RFC so i'm not sure if i'm just being picky because i'm not aware of a very good reasons pointed out there.

OK.

Any pushback re. this patch?

Thanks!

[mtrofin]

leftover fix from python tool

[mtrofin]

gentle reminder - thanks!

[mtrofin]

Gentle reminder - @jdoerfert , is blank-allowing all the Transforms/Attributor to have unused prefixes "as intended"? (I remember you indicating that was the case)

I intend to commit this on Wednesday, it's basically NFC.

Thanks!

[sstefan1]

In D92404#2436313, @mtrofin wrote:

Gentle reminder - @jdoerfert , is blank-allowing all the Transforms/Attributor to have unused prefixes "as intended"? (I remember you indicating that was the case)

Yeah that's the case.

[mtrofin]

added one more file that had unused prefixes

llvm/test/Transforms/ArgumentPromotion/crash.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S < %s -inline -argpromotion | FileCheck %s --check-prefixes=ARGPROMOTION,ALL_OLDPM
+; RUN: opt -S < %s -inline -argpromotion | FileCheck %s --check-prefix=ARGPROMOTION
 ; RUN: opt -S < %s -passes=inline,argpromotion | FileCheck %s --check-prefixes=ARGPROMOTION,ALL_NEWPM
 
 %S = type { %S* }
 
 ; Inlining should nuke the invoke (and any inlined calls) here even with
 ; argument promotion running along with it.
 define void @zot() personality i32 (...)* @wibble {
 ; ARGPROMOTION-LABEL: define {{[^@]+}}@zot() personality i32 (...)* @wibble

llvm/test/Transforms/Attributor/lit.local.cfg

+# -*- Python -*- vim: set ft=python ts=4 sw=4 expandtab tw=79:
+from lit.llvm.subst import ToolSubst
+
+fc = ToolSubst('FileCheck', unresolved='fatal')
+# the parent introduced the opposite rule, so we replace it if we see it.
+if len(config.substitutions) > 0 and config.substitutions[0] == (fc.regex, 'FileCheck --allow-unused-prefixes=false'):
+    config.substitutions[0] = (
+        fc.regex, 'FileCheck --allow-unused-prefixes=true')
+else:
+    config.substitutions.insert(0, (fc.regex, 
+                                    'FileCheck --allow-unused-prefixes=true'))

llvm/test/Transforms/HardwareLoops/scalar-while.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -S %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-DEC
-; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-hardware-loop-phi=true -S %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-PHI
-; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-nested-hardware-loop=true -S %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NESTED
-; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-hardware-loop-guard=true -S %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-GUARD
-; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-hardware-loop-phi=true -force-hardware-loop-guard=true -S %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-PHIGUARD
+; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -S %s -o - | FileCheck %s --check-prefix=CHECK-DEC
+; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-hardware-loop-phi=true -S %s -o - | FileCheck %s --check-prefix=CHECK-PHI
+; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-nested-hardware-loop=true -S %s -o - | FileCheck %s --check-prefix=CHECK-NESTED
+; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-hardware-loop-guard=true -S %s -o - | FileCheck %s --check-prefix=CHECK-GUARD
+; RUN: opt -hardware-loops -force-hardware-loops=true -hardware-loop-decrement=1 -hardware-loop-counter-bitwidth=32 -force-hardware-loop-phi=true -force-hardware-loop-guard=true -S %s -o - | FileCheck %s --check-prefix=CHECK-PHIGUARD
 
 define void @while_lt(i32 %i, i32 %N, i32* nocapture %A) {
 ; CHECK-DEC-LABEL: @while_lt(
 ; CHECK-DEC-NEXT:  entry:
 ; CHECK-DEC-NEXT:    [[CMP4:%.*]] = icmp ult i32 [[I:%.*]], [[N:%.*]]
 ; CHECK-DEC-NEXT:    br i1 [[CMP4]], label [[WHILE_BODY_PREHEADER:%.*]], label [[WHILE_END:%.*]]
 ; CHECK-DEC:       while.body.preheader:
 ; CHECK-DEC-NEXT:    [[TMP0:%.*]] = sub i32 [[N]], [[I]]

llvm/test/Transforms/Inline/inline_stats.ll

 ; First with legacy PM
-; RUN: opt -S -inline -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s -check-prefix=CHECK-BASIC -check-prefix=CHECK
-; RUN: opt -S -inline -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s -check-prefix="CHECK-VERBOSE" -check-prefix=CHECK
+; RUN: opt -S -inline -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s --check-prefixes=CHECK-BASIC,CHECK
+; RUN: opt -S -inline -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s --check-prefixes="CHECK-VERBOSE",CHECK
 
 ; Do again with new PM
-; RUN: opt -S -passes=inline -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s -check-prefix=CHECK-BASIC -check-prefix=CHECK
-; RUN: opt -S -passes=inline -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s -check-prefix="CHECK-VERBOSE" -check-prefix=CHECK
+; RUN: opt -S -passes=inline -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s --check-prefixes=CHECK-BASIC,CHECK
+; RUN: opt -S -passes=inline -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s --check-prefixes="CHECK-VERBOSE",CHECK
 
-; RUN: opt -S -passes=inliner-wrapper -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s -check-prefix=CHECK-BASIC -check-prefix=CHECK
-; RUN: opt -S -passes=inliner-wrapper -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s -check-prefix="CHECK-VERBOSE" -check-prefix=CHECK
+; RUN: opt -S -passes=inliner-wrapper -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s --check-prefixes=CHECK-BASIC,CHECK
+; RUN: opt -S -passes=inliner-wrapper -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s --check-prefixes="CHECK-VERBOSE",CHECK
 
-; RUN: opt -S -passes=always-inliner-wrapper,inliner-wrapper -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s -check-prefix=WRAPPER-BASIC -check-prefix=WRAPPER
-; RUN: opt -S -passes=always-inliner-wrapper,inliner-wrapper -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s -check-prefix=WRAPPER-VERBOSE -check-prefix=WRAPPER
+; RUN: opt -S -passes=always-inliner-wrapper,inliner-wrapper -inliner-function-import-stats=basic < %s 2>&1 | FileCheck %s -check-prefix=WRAPPER
+; RUN: opt -S -passes=always-inliner-wrapper,inliner-wrapper -inliner-function-import-stats=verbose < %s 2>&1 | FileCheck %s --check-prefixes=WRAPPER-VERBOSE,WRAPPER
 
 ; CHECK: ------- Dumping inliner stats for [<stdin>] -------
 ; CHECK-BASIC-NOT: -- List of inlined functions:
 ; CHECK-BASIC-NOT: -- Inlined not imported function
 ; CHECK-VERBOSE: -- List of inlined functions:
 ; CHECK-VERBOSE: Inlined not imported function [internal2]: #inlines = 6, #inlines_to_importing_module = 2
 ; CHECK-VERBOSE: Inlined imported function [external2]: #inlines = 4, #inlines_to_importing_module = 1
 ; CHECK-VERBOSE: Inlined imported function [external1]: #inlines = 3, #inlines_to_importing_module = 2

llvm/test/Transforms/Inline/noalias2.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
 ; RUN: opt -inline -enable-noalias-to-md-conversion -S < %s | FileCheck %s --check-prefixes=CHECK,NO_ASSUME
-; RUN: opt -inline -enable-noalias-to-md-conversion --enable-knowledge-retention -S < %s | FileCheck %s --check-prefixes=CHECK,USE_ASSUME
+; RUN: opt -inline -enable-noalias-to-md-conversion --enable-knowledge-retention -S < %s | FileCheck %s
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @hello(float* noalias nocapture %a, float* noalias nocapture readonly %c) #0 {
 ; CHECK-LABEL: define {{[^@]+}}@hello
 ; CHECK-SAME: (float* noalias nocapture [[A:%.*]], float* noalias nocapture readonly [[C:%.*]]) #0
 ; CHECK-NEXT:  entry:

llvm/test/Transforms/LICM/pr23608.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -S -licm %s | FileCheck %s --check-prefixes=CHECK,NO_ASSUME
-; RUN: opt -S -licm --enable-knowledge-retention %s | FileCheck %s --check-prefixes=CHECK,USE_ASSUME
+; RUN: opt -S -licm %s | FileCheck %s --check-prefix=NO_ASSUME
+; RUN: opt -S -licm --enable-knowledge-retention %s | FileCheck %s --check-prefix=USE_ASSUME
 ; ModuleID = '../pr23608.ll'
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 %struct.PyFrameObject = type { i32 }
 
 @a = common global %struct.PyFrameObject* null, align 8
 @__msan_origin_tls = external thread_local(initialexec) global i32

llvm/test/Transforms/LoadStoreVectorizer/AMDGPU/merge-stores-private.ll

 ; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-4,-unaligned-scratch-access  -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT4,ELT4-ALIGNED,ALIGNED,ALL %s
-; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-8,-unaligned-scratch-access  -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT8,ELT8-ALIGNED,ALIGNED,ALL %s
-; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-16,-unaligned-scratch-access -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT16,ELT16-ALIGNED,ALIGNED,ALL %s
+; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-8,-unaligned-scratch-access  -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT8,ALIGNED,ALL %s
+; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-16,-unaligned-scratch-access -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT16,ALIGNED,ALL %s
 ; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-4,+unaligned-scratch-access  -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT4,ELT4-UNALIGNED,UNALIGNED,ALL %s
 ; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-8,+unaligned-scratch-access  -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT8,ELT8-UNALIGNED,UNALIGNED,ALL %s
 ; RUN: opt -mtriple=amdgcn-amd-amdhsa -mattr=+max-private-element-size-16,+unaligned-scratch-access -load-store-vectorizer -S -o - %s | FileCheck -check-prefixes=ELT16,ELT16-UNALIGNED,UNALIGNED,ALL %s
 
 target datalayout = "e-p:64:64-p1:64:64-p2:32:32-p3:32:32-p4:64:64-p5:32:32-p6:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64-S32-A5"
 
 ; ALL-LABEL: @merge_private_store_4_vector_elts_loads_v4i32
 ; ELT4-ALIGNED: store i32

llvm/test/Transforms/LoopIdiom/X86/left-shift-until-bittest.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -debugify -loop-idiom -mtriple=x86_64 -mcpu=core-avx2 < %s -S | FileCheck -check-prefixes=ALL,LZCNT %s
-; RUN: opt -debugify -loop-idiom -mtriple=x86_64 -mcpu=corei7 < %s -S | FileCheck -check-prefixes=ALL,NOLZCNT %s
+; RUN: opt -debugify -loop-idiom -mtriple=x86_64 -mcpu=core-avx2 < %s -S | FileCheck --check-prefix=ALL %s
+; RUN: opt -debugify -loop-idiom -mtriple=x86_64 -mcpu=corei7 < %s -S | FileCheck --check-prefix=ALL %s
 
 declare i32 @gen32()
 declare void @use32(i32)
 declare void @use1(i1)
 declare void @external_side_effect()
 
 ; The patterns here are all have the same base form:
 ;   while (!(x & (1U << bit)))

 ; ALL-NEXT:    [[X_NEXT]] = shl i32 [[X_CURR]], 1, [[DBG21:!dbg !.*]]
 ; ALL-NEXT:    call void @llvm.dbg.value(metadata i32 [[X_NEXT]], [[META15:metadata !.*]], metadata !DIExpression()), [[DBG21]]
 ; ALL-NEXT:    br i1 [[X_CURR_ISBITUNSET]], label [[LOOP]], label [[END:%.*]], [[DBG22:!dbg !.*]]
 ; ALL:       end:
 ; ALL-NEXT:    [[X_CURR_LCSSA:%.*]] = phi i32 [ [[X_CURR]], [[LOOP]] ], [[DBG18]]
 ; ALL-NEXT:    call void @llvm.dbg.value(metadata i32 [[X_CURR_LCSSA]], [[META11]], metadata !DIExpression()), [[DBG18]]
 ; ALL-NEXT:    ret i32 [[X_CURR_LCSSA]], [[DBG23:!dbg !.*]]
 ;
 entry:
   %bitmask = shl i32 1, %bit
   br label %loop
 
 loop:
   %x.curr = phi i32 [ %x, %entry ], [ %x.next, %loop ]
   %x.curr.bitmasked = and i32 %x.curr, %bitmask
   %x.curr.isbitunset = icmp eq i32 %x.curr.bitmasked, 0
   %x.next = shl i32 %x.curr, 1

llvm/test/Transforms/LoopStrengthReduce/X86/lsr-insns-1.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -loop-reduce -mtriple=x86_64  -S | FileCheck %s -check-prefix=BOTH -check-prefix=INSN
-; RUN: opt < %s -loop-reduce -mtriple=x86_64 -lsr-insns-cost=false -S | FileCheck %s -check-prefix=BOTH -check-prefix=REGS
+; RUN: opt < %s -loop-reduce -mtriple=x86_64  -S | FileCheck %s -check-prefix=INSN
+; RUN: opt < %s -loop-reduce -mtriple=x86_64 -lsr-insns-cost=false -S | FileCheck %s -check-prefix=REGS
 ; RUN: llc < %s -O2 -mtriple=x86_64-unknown-unknown -lsr-insns-cost | FileCheck %s
 
 ; OPT test checks that LSR optimize compare for static counter to compare with 0.
 
 ; LLC test checks that LSR optimize compare for static counter.
 ; That means that instead of creating the following:
 ;   movl %ecx, (%rdx,%rax,4)
 ;   incq %rax

llvm/test/Transforms/LowerTypeTests/export-inline.ll

-; RUN: opt -mtriple=x86_64-unknown-linux -S -lowertypetests -lowertypetests-summary-action=export -lowertypetests-read-summary=%S/Inputs/use-typeid1-typeid2.yaml -lowertypetests-write-summary=%t < %s | FileCheck --check-prefixes=CHECK,X86 %s
+; RUN: opt -mtriple=x86_64-unknown-linux -S -lowertypetests -lowertypetests-summary-action=export -lowertypetests-read-summary=%S/Inputs/use-typeid1-typeid2.yaml -lowertypetests-write-summary=%t < %s | FileCheck --check-prefix=CHECK %s
 ; RUN: FileCheck --check-prefixes=SUMMARY,SUMMARY-X86 %s < %t
 
-; RUN: opt -mtriple=aarch64-unknown-linux -S -lowertypetests -lowertypetests-summary-action=export -lowertypetests-read-summary=%S/Inputs/use-typeid1-typeid2.yaml -lowertypetests-write-summary=%t < %s | FileCheck --check-prefixes=CHECK,ARM %s
+; RUN: opt -mtriple=aarch64-unknown-linux -S -lowertypetests -lowertypetests-summary-action=export -lowertypetests-read-summary=%S/Inputs/use-typeid1-typeid2.yaml -lowertypetests-write-summary=%t < %s | FileCheck --check-prefix=CHECK %s
 ; RUN: FileCheck --check-prefixes=SUMMARY,SUMMARY-ARM %s < %t
 
 @foo = constant [2048 x i8] zeroinitializer, !type !0, !type !1, !type !2, !type !3
 
 !0 = !{i32 0, !"typeid1"}
 !1 = !{i32 6, !"typeid1"}
 !2 = !{i32 4, !"typeid2"}
 !3 = !{i32 136, !"typeid2"}

llvm/test/Transforms/PhaseOrdering/ARM/arm_fill_q7.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -O3 -S                                        | FileCheck -check-prefixes=ALL,OLDPM %s
-; RUN: opt < %s -passes='default<O3>' -aa-pipeline=default -S | FileCheck -check-prefixes=ALL,NEWPM %s
+; RUN: opt < %s -O3 -S                                        | FileCheck --check-prefix=OLDPM %s
+; RUN: opt < %s -passes='default<O3>' -aa-pipeline=default -S | FileCheck --check-prefix=NEWPM %s
 
 target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
 target triple = "thumbv6m-none-none-eabi"
 
 ; Not only should we be able to to form memsets here, the original loops
 ; should be deleted, too.
 
 ; Function Attrs: nounwind

llvm/test/Transforms/PhaseOrdering/X86/loop-idiom-vs-indvars.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -mcpu=core-avx2 < %s -O3 -S                                        | FileCheck -check-prefixes=ALL,OLDPM %s
-; RUN: opt -mcpu=core-avx2 < %s -passes='default<O3>' -aa-pipeline=default -S | FileCheck -check-prefixes=ALL,NEWPM %s
+; RUN: opt -mcpu=core-avx2 < %s -O3 -S                                        | FileCheck --check-prefix=ALL %s
+; RUN: opt -mcpu=core-avx2 < %s -passes='default<O3>' -aa-pipeline=default -S | FileCheck --check-prefix=ALL %s
 
 ; Not only should we be able to make the loop countable,
 ; %whatever.next recurrence should be rewritten, making loop dead.
 
 target triple = "x86_64--"
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 define i32 @cttz(i32 %n, i32* %p1) {

llvm/test/Transforms/lit.local.cfg

+# -*- Python -*- vim: set ft=python ts=4 sw=4 expandtab tw=79:
+from lit.llvm.subst import ToolSubst
+
+fc = ToolSubst('FileCheck', unresolved='fatal')
+# Insert this first. Then, we'll first update the blank FileCheck command; then,
+# the default substitution of FileCheck will replace it to its full path.
+config.substitutions.insert(0, (fc.regex, 
+    'FileCheck --allow-unused-prefixes=false'))

llvm/test/lit.cfg.py

def get_asan_rtlib():
     host_lib_dir = os.path.join(os.path.dirname(config.host_cc), '../lib')
     asan_dylib_dir_pattern = host_lib_dir + \
         '/clang/*/lib/darwin/libclang_rt.asan_osx_dynamic.dylib'
     found_dylibs = glob.glob(asan_dylib_dir_pattern)
     if len(found_dylibs) != 1:
         return ''
     return found_dylibs[0]
 
+# Define this first. Afterwards, use_default_substitutions will add the rule for
+# expanding FileCheck to the full path.
+config.substitutions.append(('%FileCheckWithUnusedPrefixes%', 
+    'FileCheck --allow-unused-prefixes=true'))
 
 llvm_config.use_default_substitutions()
 
 # Add site-specific substitutions.
 config.substitutions.append(('%llvmshlibdir', config.llvm_shlib_dir))
 config.substitutions.append(('%shlibext', config.llvm_shlib_ext))
 config.substitutions.append(('%exeext', config.llvm_exe_ext))