[EraVM] Add pre-commit test for Optimize towards branch on zero in EraVMPostCodegenPrepare

Add tests where lshr/add/sub + cmp can be transformed
into lshr/add/sub + cmp eq/ne 0. This transformation
is beneficial, since lshl/add/sub produce flags and
cmp can be combined with them.

Signed-off-by: Vladimir Radosavljevic <[email protected]>

Author: vladimirradosavljevic

llvm/test/CodeGen/EraVM/branch-on-zero.ll

@@ -0,0 +1,140 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 2
+; RUN: llc -O3 < %s | FileCheck %s
+
+target datalayout = "E-p:256:256-i256:256:256-S32-a:256:256"
+target triple = "eravm"
+
+define i256 @lshr(i256 %a) {
+; CHECK-LABEL: lshr:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    sub.s! 7, r1, r2
+; CHECK-NEXT:    shr.s.gt 3, r1, r1
+; CHECK-NEXT:    add.le r0, r0, r1
+; CHECK-NEXT:    ret
+entry:
+  %c = icmp ult i256 %a, 8
+  br i1 %c, label %then, label %else
+
+then:
+  ret i256 0
+
+else:
+  %l = lshr i256 %a, 3
+  ret i256 %l
+}
+
+define i256 @lshr_not(i256 %a) {
+; CHECK-LABEL: lshr_not:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    sub.s! 7, r1, r2
+; CHECK-NEXT:    shr.s.gt 4, r1, r1
+; CHECK-NEXT:    add.le r0, r0, r1
+; CHECK-NEXT:    ret
+entry:
+  %c = icmp ult i256 %a, 8
+  br i1 %c, label %then, label %else
+
+then:
+  ret i256 0
+
+else:
+  %l = lshr i256 %a, 4
+  ret i256 %l
+}
+
+; Test where overflow intrinsic would be generated if this
+; optimization is done in the CodeGenPrepare pass.
+define i256 @add_overflow(i256 %a) {
+; CHECK-LABEL: add_overflow:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    sub.s! @CPI2_0[0], r1, r2
+; CHECK-NEXT:    add.ne 1, r1, r1
+; CHECK-NEXT:    add.eq r0, r0, r1
+; CHECK-NEXT:    ret
+entry:
+  %c = icmp eq i256 %a, -1
+  br i1 %c, label %then, label %else
+
+then:
+  ret i256 0
+
+else:
+  %l = add i256 %a, 1
+  ret i256 %l
+}
+
+define i256 @add(i256 %a) {
+; CHECK-LABEL: add:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    sub.s! 10, r1, r2
+; CHECK-NEXT:    sub.s.ne 10, r1, r1
+; CHECK-NEXT:    add.eq r0, r0, r1
+; CHECK-NEXT:    ret
+entry:
+  %c = icmp eq i256 %a, 10
+  br i1 %c, label %then, label %else
+
+then:
+  ret i256 0
+
+else:
+  %l = add i256 %a, -10
+  ret i256 %l
+}
+
+define i256 @add_not(i256 %a) {
+; CHECK-LABEL: add_not:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    sub.s! 10, r1, r2
+; CHECK-NEXT:    add.ne 10, r1, r1
+; CHECK-NEXT:    add.eq r0, r0, r1
+; CHECK-NEXT:    ret
+entry:
+  %c = icmp eq i256 %a, 10
+  br i1 %c, label %then, label %else
+
+then:
+  ret i256 0
+
+else:
+  %l = add i256 %a, 10
+  ret i256 %l
+}
+
+define i256 @sub(i256 %a) {
+; CHECK-LABEL: sub:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    sub.s! 10, r1, r2
+; CHECK-NEXT:    sub.s.ne 10, r1, r1
+; CHECK-NEXT:    add.eq r0, r0, r1
+; CHECK-NEXT:    ret
+entry:
+  %c = icmp eq i256 %a, 10
+  br i1 %c, label %then, label %else
+
+then:
+  ret i256 0
+
+else:
+  %l = sub i256 %a, 10
+  ret i256 %l
+}
+
+define i256 @sub_not(i256 %a) {
+; CHECK-LABEL: sub_not:
+; CHECK:       ; %bb.0: ; %entry
+; CHECK-NEXT:    sub.s! 10, r1, r2
+; CHECK-NEXT:    add.ne 10, r1, r1
+; CHECK-NEXT:    add.eq r0, r0, r1
+; CHECK-NEXT:    ret
+entry:
+  %c = icmp eq i256 %a, 10
+  br i1 %c, label %then, label %else
+
+then:
+  ret i256 0
+
+else:
+  %l = sub i256 %a, -10
+  ret i256 %l
+}