Legalize neg: -x becomes 0 - x (#2128)

This fixes an error with negating a negative SInt literal and a
[debatable] lint warning in Verilator when negating any value.

This behavior matches that of Chisel (which directly emits the 0 - x
already).

1 files changed, 22 insertions, 0 deletions

diff --git a/src/test/resources/passes/Legalize/Legalize.fir b/src/test/resources/passes/Legalize/Legalize.fir
index 7e538695..a0a39845 100644
--- a/src/test/resources/passes/Legalize/Legalize.fir
+++ b/src/test/resources/passes/Legalize/Legalize.fir
@@ -39,3 +39,25 @@ circuit Legalize :
     when neq(bar_15, UInt(1)) :
       printf(clock, UInt(1), "Assertion failed!\n bar_15 != 0\n")
       stop(clock, UInt(1), 1)
+
+    ; Check neg of literals
+    node negUInt0 = neg(UInt(123))
+    when neq(negUInt0, SInt(-123)) :
+      printf(clock, UInt(1), "Assertion failed!\n negUInt0 != -123\n")
+      stop(clock, UInt(1), 1)
+    node negUInt1 = neg(UInt<8>(0))
+    when neq(negUInt1, SInt<8>(0)) :
+      printf(clock, UInt(1), "Assertion failed!\n negUInt1 != 0\n")
+      stop(clock, UInt(1), 1)
+    node negSInt0 = neg(SInt(123))
+    when neq(negSInt0, SInt(-123)) :
+      printf(clock, UInt(1), "Assertion failed!\n negSInt0 != -123\n")
+      stop(clock, UInt(1), 1)
+    node negSInt1 = neg(SInt(-123))
+    when neq(negSInt1, SInt(123)) :
+      printf(clock, UInt(1), "Assertion failed!\n negSInt1 != 123\n")
+      stop(clock, UInt(1), 1)
+    node negSInt2 = neg(SInt(0))
+    when neq(negSInt2, SInt(0)) :
+      printf(clock, UInt(1), "Assertion failed!\n negSInt2 != 0\n")
+      stop(clock, UInt(1), 1)