[PATCH v3 01/23] perf expr: Allow a double if expression

[Ian Rogers <irogers@google.com>]

Some TMA metrics have double if expressions like:
( CPU_CLK_UNHALTED.THREAD / 2 ) * ( 1 + CPU_CLK_UNHALTED.ONE_THREAD_ACTIVE / CPU_CLK_UNHALTED.REF_XCLK ) ) if #core_wide < 1 else ( CPU_CLK_UNHALTED.THREAD_ANY / 2 ) if #SMT_on else CPU_CLK_UNHALTED.THREAD
This currently fails to parse as the left hand side if expression needs
to be in parentheses. By allowing the if expression to have a right hand
side that is an if expression we can parse the expression above, with
left to right evaluation order that matches languages like Python.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/expr.c | 4 ++++
 tools/perf/util/expr.y  | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/expr.c b/tools/perf/tests/expr.c
index 8bd719766814..6512f5e22045 100644
--- a/tools/perf/tests/expr.c
+++ b/tools/perf/tests/expr.c
@@ -95,6 +95,10 @@ static int test__expr(struct test_suite *t __maybe_unused, int subtest __maybe_u
 	ret |= test(ctx, "min(1,2) + 1", 2);
 	ret |= test(ctx, "max(1,2) + 1", 3);
 	ret |= test(ctx, "1+1 if 3*4 else 0", 2);
+	ret |= test(ctx, "100 if 1 else 200 if 1 else 300", 100);
+	ret |= test(ctx, "100 if 0 else 200 if 1 else 300", 200);
+	ret |= test(ctx, "100 if 1 else 200 if 0 else 300", 100);
+	ret |= test(ctx, "100 if 0 else 200 if 0 else 300", 300);
 	ret |= test(ctx, "1.1 + 2.1", 3.2);
 	ret |= test(ctx, ".1 + 2.", 2.1);
 	ret |= test(ctx, "d_ratio(1, 2)", 0.5);
diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index a30b825adb7b..635e562350c5 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -156,7 +156,7 @@ start: if_expr
 }
 ;
 
-if_expr: expr IF expr ELSE expr
+if_expr: expr IF expr ELSE if_expr
 {
 	if (fpclassify($3.val) == FP_ZERO) {
 		/*
-- 
2.38.0.rc1.362.ged0d419d3c-goog