[NFC][StackSafety] Test that StackLifetime looks through stripPointerCasts

[ChuanqiXu]

Summary

StackLifetime class collects lifetime marker of an alloca by collect
the user of BitCast who is the user of the alloca. However, either
the alloca itself could be used with the lifetime marker or the BitCast
of the alloca could be transformed to other instructions. (e.g.,
it may be transformed to all zero reps in InstCombine pass).
This patch tries to fix this process in collectMarkers functions.

[RKSimon]

test case?

[ChuanqiXu]

This comment was removed by ChuanqiXu.

[ChuanqiXu]

Update test case

[ChuanqiXu]

In D85399#2199566, @RKSimon wrote:

test case?

Sorry, it's my fault to forget to update the test case. I update it now. The IR in the test file is generated by command clang -O2 -S -emit-llvm for the following code:

typedef struct  {
    char a[500];
} char_array;

void consume(char_array);

void simple(int cond) {
    if (cond) {
        char_array a;
        consume(a);
    } else {
        char_array b;
        consume(b);
    }
}

[ChuanqiXu]

@RKSimon , gentle ping~

[vitalybuka]

This function was changed
Is this issue still relevant?
If this is still needed, could you please make this a regular lit test?

[ChuanqiXu]

In D85399#2223309, @vitalybuka wrote:

This function was changed
Is this issue still relevant?
If this is still needed, could you please make this a regular lit test?

Thanks for your comment. This issue is fixed by the new commit. I don't know how to add this a regular lit test because StackLifetime module won't provide a pass interface, which means I can call it from opt.

[vitalybuka]

The test is still could be useful
Maybe something like this llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll ?

[ChuanqiXu]

In D85399#2223329, @vitalybuka wrote:

The test is still could be useful
Maybe something like this llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll ?

Oh, I find here is StackLifetimePrinterPass which I can use for tests. I updated the diff about test case to lifetime.ll for now.

[vitalybuka]

cleanup

[vitalybuka]

LGTM with some updates

[ChuanqiXu]

In D85399#2225025, @vitalybuka wrote:

LGTM with some updates

Thank you very much !!!

llvm/test/Analysis/StackSafetyAnalysis/lifetime.ll

 ; RUN: opt -passes='print<stack-lifetime><may>' -disable-output %s 2>&1 | FileCheck %s --check-prefixes=CHECK,MAY
 ; RUN: opt -passes='print<stack-lifetime><must>' -disable-output %s 2>&1 | FileCheck %s --check-prefixes=CHECK,MUST
 
+%struct.char_array = type { [500 x i8] }
+
+; Function Attrs: nounwind uwtable
+define dso_local void @foo(i32 %cond) local_unnamed_addr #0 {
+entry:
+  %a = alloca %struct.char_array, align 8
+  %b = alloca %struct.char_array, align 8
+  %tobool.not = icmp eq i32 %cond, 0
+  br i1 %tobool.not, label %if.else, label %if.then
+
+if.then:                                          ; preds = %entry
+  %0 = getelementptr inbounds %struct.char_array, %struct.char_array* %a, i64 0, i32 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 500, i8* nonnull %0) #3
+  tail call void @consume(%struct.char_array* nonnull byval(%struct.char_array) align 8 %a) #3
+; CHECK: ; Alive: <a>
+  call void @llvm.lifetime.end.p0i8(i64 500, i8* nonnull %0) #3
+  br label %if.end
+
+if.else:                                          ; preds = %entry
+  %1 = getelementptr inbounds %struct.char_array, %struct.char_array* %b, i64 0, i32 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 500, i8* nonnull %1) #3
+  tail call void @consume(%struct.char_array* nonnull byval(%struct.char_array) align 8 %b) #3
+; CHECK: ; Alive: <b>
+  call void @llvm.lifetime.end.p0i8(i64 500, i8* nonnull %1) #3
+  br label %if.end
+
+if.end:                                           ; preds = %if.else, %if.then
+  ret void
+}
+
+declare dso_local void @consume(%struct.char_array* byval(%struct.char_array) align 8) local_unnamed_addr #2
+
 define void @f() {
 ; CHECK-LABEL: define void @f()
 entry:
 ; CHECK: entry:
 ; CHECK-NEXT: Alive: <>
   %x = alloca i32, align 4
   %y = alloca i32, align 4
 ; CHECK: %y = alloca i32, align 4