[llvm] [BOLT][RISCV] Fix conditional tail call (PR #209474)

[Craig Topper via llvm-commits]

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@@ -0,0 +1,65 @@
+// Check that all base and compressed RISC-V conditional branches targeting
+// another function are expanded to tail-call blocks, survive block reordering,
+// and are emitted with the correct target.
+
+// RUN: llvm-mc -triple riscv64 -mattr=+c -filetype=obj -o %t.o %s
+// RUN: ld.lld -o %t %t.o
+// RUN: llvm-bolt %t -o %t.bolt --reorder-blocks=reverse --print-cfg \
+// RUN:   --print-only=conditional_tail_calls 2>&1 | FileCheck %s
+// RUN: llvm-objdump -d --disassemble-symbols=conditional_tail_calls %t.bolt \
+// RUN:   | FileCheck %s --check-prefix=DISASM
+
+// CHECK: Binary Function "conditional_tail_calls" after building cfg {
+// CHECK:      beq a0, a1, .LTC0
+// CHECK:      bne a0, a1, .LTC1
+// CHECK:      blt a0, a1, .LTC2
+// CHECK:      bge a0, a1, .LTC3
+// CHECK:      bltu a0, a1, .LTC4
+// CHECK:      bgeu a0, a1, .LTC5
+// CHECK:      beqz a0, .LTC6
+// CHECK:      bnez a0, .LTC7
+// CHECK: BOLT-INFO: basic block reordering modified layout of 1 functions
+
+// DISASM-LABEL: <conditional_tail_calls>:
+// DISASM-NEXT: {{.*}} beq a0, a1, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} bne a0, a1, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} blt a0, a1, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} bge a0, a1, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} bltu a0, a1, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} bgeu a0, a1, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} beqz a0, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} bnez a0, {{.*}} <callee>
+// DISASM-NEXT: {{.*}} ret
+
+  .text
+  .option rvc
+
+  .globl conditional_tail_calls
+  .type conditional_tail_calls, @function
+  .p2align 1
+conditional_tail_calls:
+  beq a0, a1, .Lcallee
----------------
topperc wrote:

why do we jump to a local label in the callee. Wouldn't a conditional tail call jump to the function label?

https://github.com/llvm/llvm-project/pull/209474