[attrs] Move the norecurse deduction to operate on the node set rather

than the SCC object, and have it scan the instruction stream directly
rather than relying on call records.

This makes the behavior of this routine consistent between libc routines
and LLVM intrinsics for libc routines. We can go and start teaching it
about those being norecurse, but we should behave the same for the
intrinsic and the libc routine rather than differently. I chatted with
James Molloy and the inconsistency doesn't seem intentional and likely
is due to intrinsic calls not being modelled in the call graph analyses.

This also fixes a bug where we would deduce norecurse on optnone
functions, when generally we try to handle optnone functions as-if they
were replaceable and thus unanalyzable.

llvm-svn: 260813

2 files changed, 8 insertions, 3 deletions

diff --git a/llvm/test/Transforms/FunctionAttrs/norecurse.ll b/llvm/test/Transforms/FunctionAttrs/norecurse.ll
index d5a2d820840..221b539655a 100644
--- a/llvm/test/Transforms/FunctionAttrs/norecurse.ll
+++ b/llvm/test/Transforms/FunctionAttrs/norecurse.ll
@@ -29,6 +29,13 @@ define i32 @extern() {
 }
 declare i32 @k() readnone
 
+; CHECK: define void @intrinsic(i8* nocapture %dest, i8* nocapture readonly %src, i32 %len) {
+define void @intrinsic(i8* %dest, i8* %src, i32 %len) {
+  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src, i32 %len, i32 1, i1 false)
+  ret void
+}
+declare void @llvm.memcpy.p0i8.p0i8.i32(i8*, i8*, i32, i32, i1)
+
 ; CHECK: define internal i32 @called_by_norecurse() #0
 define internal i32 @called_by_norecurse() {
   %a = call i32 @k()
diff --git a/llvm/test/Transforms/FunctionAttrs/optnone.ll b/llvm/test/Transforms/FunctionAttrs/optnone.ll
index 441ff4da65e..cd08c75d75b 100644
--- a/llvm/test/Transforms/FunctionAttrs/optnone.ll
+++ b/llvm/test/Transforms/FunctionAttrs/optnone.ll
@@ -16,11 +16,9 @@ define void @test_optnone(i8* %p) noinline optnone {
 
 declare i8 @strlen(i8*) noinline optnone
 ; CHECK-LABEL: @strlen
-; CHECK: (i8*) #2
+; CHECK: (i8*) #1
 
 ; CHECK-LABEL: attributes #0
 ; CHECK: = { norecurse readnone }
 ; CHECK-LABEL: attributes #1
-; CHECK: = { noinline norecurse optnone }
-; CHECK-LABEL: attributes #2
 ; CHECK: = { noinline optnone }