[RISCV] Add test describing constant materialisation problem in loops

[luke]

Summary

As @alexey-bataev noticed, with the current cost model we account for
the cost of constant materialisation through the user's instruction
cost.
For straight line code this is usually fine, but inside a loop these
constants are usually hoisted out by LICM.
They should probably not be accounted for in these cases.

[luke]

The cost model will probably need a bit of reworking, and I'm not sure if these constant materialisation costs will end up being factored out of getInstructionCost or if there will be some other interface, so these tests are not that useful as it stands.

llvm/test/Analysis/CostModel/RISCV/const-loop.ll

+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes="print<cost-model>" 2>&1 -disable-output -mtriple=riscv64 -mattr=+v,+f,+d,+zfh,+experimental-zvfh -riscv-v-vector-bits-min=128 -riscv-v-fixed-length-vector-lmul-max=1 < %s | FileCheck %s
+; Check that we don't crash querying costs when vectors are not enabled.
+; RUN: opt -passes="print<cost-model>" 2>&1 -disable-output -mtriple=riscv64
+
+; FIXME: These tests include instructions that account for the cost of constant
+; materialisation in their own cost. However in practice, because they are in a
+; loop, these constants are hoisted out by LICM, and should probably be ignored.
+
+define void @add_v4i32(ptr %p) {
+; CHECK-LABEL: 'add_v4i32'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i = phi i32 [ 0, %entry ], [ %i.next, %loop ]
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %q = getelementptr <4 x i32>, ptr %p, i32 %i
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %x = load <4 x i32>, ptr %q, align 16
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %y = add <4 x i32> %x, <i32 256, i32 4096, i32 57, i32 1>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: store <4 x i32> %y, ptr %q, align 16
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i.next = add i32 %i, 1
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %done = icmp eq i32 %i, 1024
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br i1 %done, label %exit, label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
+;
+entry:
+  br label %loop
+loop:
+  %i = phi i32 [0, %entry], [%i.next, %loop]
+  %q = getelementptr <4 x i32>, ptr %p, i32 %i
+  %x = load <4 x i32>, ptr %q
+  %y = add <4 x i32> %x, <i32 256, i32 4096, i32 57, i32 1>
+  store <4 x i32> %y, ptr %q
+  %i.next = add i32 %i, 1
+  %done = icmp eq i32 %i, 1024
+  br i1 %done, label %exit, label %loop
+exit:
+  ret void
+}
+
+define void @store_v4i32(ptr %p) {
+; CHECK-LABEL: 'store_v4i32'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i = phi i32 [ 0, %entry ], [ %i.next, %loop ]
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %q = getelementptr <4 x i32>, ptr %p, i32 %i
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: store <4 x i32> <i32 256, i32 4096, i32 57, i32 1>, ptr %q, align 16
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i.next = add i32 %i, 1
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %done = icmp eq i32 %i, 1024
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br i1 %done, label %exit, label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
+;
+entry:
+  br label %loop
+loop:
+  %i = phi i32 [0, %entry], [%i.next, %loop]
+  %q = getelementptr <4 x i32>, ptr %p, i32 %i
+  store <4 x i32> <i32 256, i32 4096, i32 57, i32 1>, ptr %q
+  %i.next = add i32 %i, 1
+  %done = icmp eq i32 %i, 1024
+  br i1 %done, label %exit, label %loop
+exit:
+  ret void
+}
+
+define void @phi_v2i64(ptr noalias %p, ptr noalias %q) {
+; CHECK-LABEL: 'phi_v2i64'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i = phi i32 [ 0, %entry ], [ %i.next, %loop.2 ]
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %p.i = getelementptr i32, ptr %p, i32 %i
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %l = load i32, ptr %p.i, align 4
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %cond = icmp eq i32 %l, 0
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br i1 %cond, label %left, label %right
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop.2
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop.2
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %x = phi <2 x i64> [ <i64 42, i64 123>, %left ], [ <i64 234, i64 1234>, %right ]
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %q.vec = getelementptr <2 x i64>, ptr %q, i32 %i
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: store <2 x i64> %x, ptr %q.vec, align 16
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i.next = add i32 %i, 1
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %done = icmp eq i32 %i, 1024
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br i1 %done, label %end, label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
+;
+entry:
+  br label %loop
+loop:
+  %i = phi i32 [0, %entry], [%i.next, %loop.2]
+  %p.i = getelementptr i32, ptr %p, i32 %i
+  %l = load i32, ptr %p.i
+  %cond = icmp eq i32 %l, 0
+  br i1 %cond, label %left, label %right
+left:
+  br label %loop.2
+right:
+  br label %loop.2
+loop.2:
+  %x = phi <2 x i64> [<i64 42, i64 123>, %left], [<i64 234, i64 1234>, %right]
+  %q.vec = getelementptr <2 x i64>, ptr %q, i32 %i
+  store <2 x i64> %x, ptr %q.vec
+  %i.next = add i32 %i, 1
+  %done = icmp eq i32 %i, 1024
+  br i1 %done, label %end, label %loop
+end:
+  ret void
+}
+
+
+define void @phi_i32(ptr noalias %p, ptr noalias %q) {
+; CHECK-LABEL: 'phi_i32'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i = phi i32 [ 0, %entry ], [ %i.next, %loop.2 ]
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %p.i = getelementptr i32, ptr %p, i32 %i
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %l = load i32, ptr %p.i, align 4
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %cond = icmp eq i32 %l, 0
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br i1 %cond, label %left, label %right
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop.2
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %loop.2
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %x = phi i32 [ 12341234, %left ], [ 84838383, %right ]
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %q.vec = getelementptr i32, ptr %q, i32 %i
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: store i32 %x, ptr %q.vec, align 4
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %i.next = add i32 %i, 1
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %done = icmp eq i32 %i, 1024
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br i1 %done, label %end, label %loop
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
+;
+entry:
+  br label %loop
+loop:
+  %i = phi i32 [0, %entry], [%i.next, %loop.2]
+  %p.i = getelementptr i32, ptr %p, i32 %i
+  %l = load i32, ptr %p.i
+  %cond = icmp eq i32 %l, 0
+  br i1 %cond, label %left, label %right
+left:
+  br label %loop.2
+right:
+  br label %loop.2
+loop.2:
+  %x = phi i32 [12341234, %left], [84838383, %right]
+  %q.vec = getelementptr i32, ptr %q, i32 %i
+  store i32 %x, ptr %q.vec
+  %i.next = add i32 %i, 1
+  %done = icmp eq i32 %i, 1024
+  br i1 %done, label %end, label %loop
+end:
+  ret void
+}